->'''Graham:''' Videogames are an escape. So invent your own fantastical calendar system and let the player know where your game takes place on it. With no frame of reference on when that is, or why you are telling them, they can't help but be drawn in!\\
'''Paul:''' Is it the past? The future? Only you will know.
-->-- '''WebVideo/{{Unskippable}} Guide to Making Cutscenes'''

In SpeculativeFiction, it's common to use a different calendar than the real world. This makes it clear to the reader that the story takes place either in another world, or in a version of our world so far in the future that time isn't even counted the same way. This also elegantly sidesteps the problems of ExtyYearsFromNow.

In fantasy, a popular version of this is to measure time in "moons" instead of months. In some cases, the author will actually have twelve different names of the form "______ Moon" to replace the twelve months of the Gregorian calendar. Nonetheless, there are actually somewhat more than twelve lunar months in an Earth year. Real lunisolar calendars solve that problem by adding a leap month to certain years; some purely lunar calendars (like the Islamic one) ignore the solar year altogether and just declare twelve lunar months to be a year.

When an Alternative Calendar is used to measure the progress of "days", it's common for characters to use {{Microts}} as smaller, more manageable units of time. In Sci-fi settings, these calendars are frequently used across multiple worlds, becoming StandardTimeUnits.

If Alternative Calendar is used in ScienceFiction with Earthian years, it may mean that the work takes place AfterTheEnd or something else that HitSoHardTheCalendarFeltIt or that everybody have OutgrownSuchSillySuperstitions and chose something significant for their reference point.

A common Year One, Day One in science fiction is October 4, 1957--the date Sputnik was launched, thereby beginning the Space Age.


[[folder:Anime & Manga]]
[[ValuesDissonance As the Japanese have a history of doing this in their own history, this trope appears a lot in anime]]. Even when depicting cultures which are not Japanese.
* Every ''Franchise/{{Gundam}}'' series except ''Gundam 00'' uses this; indeed, the various calendars are a common way of differentiating between {{Alternate Universe}}s.
** [[FollowTheLeader As a direct result]] of ''[[Anime/MobileSuitGundam Gundam 0079]]'''s success with the Universal Century calendar, this trope can also be found in the majority of RealRobot series produced since.
** Based on a couple of instances where concrete dates are given in ''0080'' and ''ZZ'', which reveal that January 14th 0080 fell on a Monday and the UC years that are multiples of 4 are leap years, respectively, it's possible to narrow down the year the changeover happened somewhat. Working backwards 79 years (no official timeline ever mentions a year UC 0000), we find that the calendar changed during a common year starting on a Tuesday, meaning the earliest possible candidate for UC 0001, as of this writing, would be 2019 (unlikely to say the least). {{Fanon}} tends to put it sometime between 2047[[note]]the last official timeline Sunrise ever published that featured dates in the AD era had 2045 as the last one mentioned, but this is apparently no longer canon[[/note]] and 2081. Of course, this all assumes that no dates were skipped over when they changed the calendar and that leap years are still calculated the same way.
** The ''[[Anime/MobileSuitGundamWing Gundam Wing]]'' sequel novel ''Frozen Teardrop'' features the first Alternate Calendar within a series: while the Earth Sphere uses the AC (After Colony) calendar, Mars uses the MC (Mars Century) calendar, with years roughly double the length of Earth's. This makes it more than a little confusing as to when exactly ''Frozen Teardrop'' takes place in relation to the main series (for the record, MC 0022 corresponds to the early 220s in AC).
** ''Anime/GundamReconguistaInG'' also does this, with the Regild Century replacing the Universal Century 1014 years before the series start.
* ''Manga/{{Gunnm}}'', particularly the space colonies in ''Last Order'' uses a calendar dating from the launch of Sputnik in 1957 AD.
* ''Anime/ValvraveTheLiberator'' which is basically Anime/MobileSuitGundamSeed + a little ''Anime/LegendOfGalacticHeroes'' with [[spoiler:SPACE VAMPIRE ILLUMINATI]] has the True Calendar.
* ''Anime/KiddyGrade'' takes place in "Star Century 0165". The reckoning is assumed to be the founding of the Galactic Union.
* ''Manga/OutlawStar'' and ''Anime/AngelLinks'' (same universe) use the TS or "Toward the Stars" calendar. ''Outlaw Star'' takes place in TS 0158. The reckoning is assumed to be the advent of interstellar travel.
* ''Anime/CodeGeass'' takes place in the year 2017 a.t.b ("Ascension Throne Britannia"), counting from the establishment of the first Celtic King in the Britannian royal line, rather than the birth of Christ. The EU uses the Revolutionary Calendar, a variant of the French Republican Calendar that sets its first year to 1790, the year after the French Revolution.
* ''Franchise/LyricalNanoha'' uses the old and new Mid-Childan calendar, [[YearZero with the new one starting]] sometime after the end of the Ancient Belkan War, when {{Magitek}} replaced physical-based weapons as the standard due to the devastation the latter caused. Interesting in that they ''also'' use the regular Earth calendar, thanks to worldhopping. The series began in year 65 of the new Mid-Childan calendar.[[note]]A common fan theory estimates that the New Calendar began around 1942 by Terran reckoning, so 0065 NC corresponds to 2006 CE.[[/note]]
* ''Anime/TheGirlWhoLeaptThroughSpace'' is set in the year 311 O.E., or the Orbital Era, counting from when humanity began living in a space colony orbiting Earth as well as on the planet itself.
* ''Anime/LibraryWar'' takes place in the year 2019 CE, which is also year 31 of the fictional Seika era (see below on the Japanese era system) -- Seika was one of the choices considered for the era following Shōwa, and in real life was discarded in favour of Heisei.
* The Magic World of ''Manga/MahouSenseiNegima'' has its own Imperial Calendar to differentiate it from the real world. The series takes place at around the year 1018 of that calendar, which is around 2003 of ours.
* ''Manga/HyperPolice'' takes place in the "22nd Year of the Holy Century".
* ''Anime/StrainStrategicArmoredInfantry'' has S.E., although we aren't really sure what it stands for. (According to the dub, it's Standard Era, but how canonical that is is debatable.)
* In ''Anime/LegendOfGalacticHeroes'', which takes place in the late 36th century AD, a new calendar (the Universal Calendar) was started when humanity left Earth and founded the Galactic Federation. The Galactic Empire replaced the Universal Calendar with a calendar counting from the year of its founding; when the Free Planets Alliance broke off, they restored it. Hence the two sides have different time reckonings.
* ''Anime/SoundOfTheSky'' starts in the spring of 271 A.P. and ends in February the following year. While not explicitly stated, it is presumably 271 years after the huge world war ended.
* ''Manga/DragonBall'' takes place on a planet called Earth, but they follow an alternative calendar (the year Goku meets Bulma is given as 749), the life-forms are full of {{Talking Animal}}s, and it's home to the titular wish-granting Dragon Balls.
* ''Anime/TigerAndBunny'' begins in 1977 N.C. (New Century). The only hint as to the real-world date would be the show's pilot, which makes mention of the 22nd century.
* Some anime (particularly those meant to be set in Japan) are noted for emphasizing use of the Japanese style of years (based on the Emperors) rather than the Western straight numeric year (see the "Real Life" section). ''VideoGame/GateKeepers'' used it for the year (it was set in 39 Showa--1969). The intro to ''Anime/PhantomQuestCorp'' also interestingly used the formal dating ("Fourth Year of the Heisei Period" instead of 1993).
* ''Anime/TekkamanBlade'' takes place in the year 192 of the Allied Earth Calendar.
* ''LightNovel/TheFamiliarOfZero'' has a 384-day calendar divided into twelve months of four eight-day weeks. Each week in the month has its own name, in addition to the months and days of the week.
* ''Soukaizan'' and ''Seikaizan'' is stated in the ''Anime/MashinHeroWataruSeries'' [[AllThereInTheManual manual]] to have different terminologies for their calendars. The date and year counts are written universally in Chinese "upper case" [[https://en.m.wikipedia.org/wiki/Chinese_numerals numerical text]] [[note]]The upper case variant is used for contemporary financal documentation as per TheOtherWiki’s example. The Japanese kanji system uses a form of simplified variety of the upper case.[[/note]], as for months, ''Soukaizan'' goes by EasternZodiac for their months ("Rat" equals January, and so forth), while ''Seikaizan'' goes by something along the lines of astrology, but their pattern wasn't fully elaborated.

[[folder:Comic Books]]
* In a ''ComicStrip/CalvinAndHobbes'' strip Calvin says that the U.S. was founded roughly around 200 B.C. - "Before Calvin".
* The world of ''ComicBook/NikolaiDante'' generally uses the Gregorian Calendar, but refers to each year as 'Year of the Tsar'.
* In ''[[ComicBook/TheMultiversity Thunderworld #1]]'', Dr. Sivana attempts to add a new calendar day called "Sivanaday", but it only lasts eight hours.

[[folder:Fan Works]]
* The ''Central Shadow Realm'' fanfiction series counts from a randomly-chosen point during the construction of the titular city; those living in the city admit it's arbitrary. The months and days don't have names; dates are given as "The (x) day of the (x) month". The first story, ''[[http://www.fanfiction.net/s/2444579/1/Shadow_Realm_Fifteen Shadow Realm: Fifteen]]'', took place in 5178.
* The ''Magick Knight: Guardian Seed'' fanfic uses the "Era of Magick" calendar, originally adopted by the "League of Nations" after the discovery of the Plants to the west and the proliferation of Adepts. Progress through the year is measured in the seasons, Winter (December-January-February), Spring (March-April-May), Summer (June-July-August) and Autumn (September-October-November). [[http://www.fanfiction.net/s/5136564/1/Magick_Knight_Guardian_Seed The story]] takes place in 70th Year of the Era of Magick.
* In ''Fanfic/FromBajorToTheBlack'', dates by the Bajoran calendar go like "Satar 4, Seventh Era 943, Year of the Unseen Harp." The date in Earth years is given nearby.
* In ''Fanfic/TheElementsOfFriendship'', the {{Cult}} of Pi, who worshipped Discord, also used their own system of telling time -- their weeks were composed of only five days (Sweetmorn, Boomtime, Pungenday, Prickle-Prickle, and Setting Orange), and their years only had five months (Chaos, Discord, Confusion, Bureaucracy, and The Aftermath), each 73 days long. And the calendar's starting point was at Discord's arrival in Equestria, which was listed as YOLD (Year of Our Lord Discord). All of this is based on the real-life Discordian calendar mentioned below.
* The Null Verse of ''FanFic/ADragonInShiningArmour'' has its own calendar known as the Golden Calendar, which is based off the Four Holy Beasts and their Devas.

* Played for laughs in ''Film/SantaClausConquersTheMartians'':
-->'''Chochem:''' What time of year is it now?\\
'''Kimar:''' It is the middle of Septober.
* In ''Film/{{Waterworld}}'', the Smokers speak of "lunars" of time. It's probably safe to assume they refer to lunar cycles. If the film takes place in waters where there is no visible seasonal cycle (and thus no way to determine the length of the year), a lunar calendar is likely the best one can develop.
* Perhaps to help correct the earlier CanonDiscontinuity, in the ''Film/StarTrek'' reboot, the Stardate calendar they use is a cross between the old universe's Stardate system and good-old-fashioned Gregorian. Stardates from this point went XX.Y, where XX was simply the Earth AD year and Y was the numerical day in that year starting from 1 (New Year's).

* Literature/ChungKuo by David Wingrove has erased all traces of the world's real past, including the birth of Christ.
* Literature/TheDraka: The Draka introduce a new [[http://en.wikipedia.org/wiki/The_Domination calender]] after winning the Final War.
* Creator/IsaacAsimov:
** In the ''Literature/{{Foundation}}'' series, the calendar begins thousands of years before the stories, with the founding date of the Galactic Empire, and later there's a new calendar that begins with the first year of the titular Foundation.
** One of the later ''Foundation'' novels is notable for having a historian discuss calendars with a companion who's looking for EarthThatWas. The historian has determined that, based on his studies, the planet must have a yearly cycle of 365 days with each day being exactly 24 hours, based on the system that's been in use by humans since time immemorial. None of the planets in the catalog match those criteria.
** Averted in ''Literature/TheEndOfEternity'', even though an Alternative Calendar would make just as much sense as it does in the Foundation series. In that book, characters will refer to "the 78th Century", "the 482nd Century", or even "a Century in the 30,000s" (i.e. 3 million years after the present), and these are dates expressed in terms of our very own Gregorian calendar. The character Cooper is from the 78th century, and although he's familiar with the idea that the year he comes from is some number in the 7700s, he apparently needed an explanation to understand why there were centuries before the 1st Century. With situations like this, you can see why this trope makes sense in fiction: because if you take a long enough view, it seems very probable that it will become TruthInTelevision.
** A couple of Asimov's stories referred to a calendar starting with 1945 - Nuclear Age, that is. In one of them it is a plot point, because [[spoiler:an angel manages to delay the end of the world by pointing out that there it must come on a certain Earth day, and without a single calendar for all, there is no such thing. So, Satan decides to strike back.]]
** Another Asimov story involves people from "our world" encountering people from a German-speaking parallel Earth which counts their calendar ''nach Hitler'' -- "after Hitler". The year turns out to be "Zwei tausend drei hundert vier-und-sechzig nach Hitler" (i.e. 2364 NH) -- apparently that's long enough that their culture is no longer Nazi-like; they readily abandon their claim to an uninhabited third Earth simply because the protagonists' world got there first. The introduction of the Nazi-descended world may be simply a pun of sorts on the story title: "Living Space" ("Lebensraum" in German).
* Steven Brust's ''Literature/{{Dragaera}}'' novels use "in the Xth year of the reign of Empress Zerika" (or whoever's on the throne). For more formal dating, they also have a more complicated system of Great Cycles, Cycles, Reigns, Phases, Turns, and Years; each (save "reign") is exactly 17 of the next stage down, and the entire calendar starts with the formation of the empire. Weeks are five days.
* Creator/DavidEddings' ''Literature/TheBelgariad'' uses the Alorn Calendar, which measures time in years since the cracking of the world. The Alorn calendar also measures their year in seasons instead of months. Additional calendars used by other nations are occasionally mentioned throughout the series.
* Creator/FrankHerbert's ''Franchise/{{Dune}}'' dates events from the establishment of the Spacing Guild's monopoly on space travel; the original novel ''Literature/{{Dune}}'' begins in the year 10,191 A.G. In addition, in ''Literature/GodEmperorOfDune'', it's implied that the (3000-year) reign of the titular God Emperor Leto II has in effect become a calendar. The prequels written by his son and Creator/KevinJAnderson avoid going into the pre-Guild calendar by having the events simply be compiled and retold by Irulan, so naturally she uses the same calendar, with the dates being B.G. (Before Guild).
* ''Literature/BraveNewWorld'' reckons its time from the completion of Henry Ford's first Model T[[note]]AD 1908[[/note]] ("in the year of our Ford"), as part of its satire of the post-Industrial Revolution world. Ironic, considering that Ford himself said "History is bunk," and is quoted as such in the book.
* The glossary of Robert Jordan's ''Literature/TheWheelOfTime'' books states that the world is on the third or fourth calendar since Rand, in a [[{{Reincarnation}} previous life]], [[TheEndOfTheWorldAsWeKnowIt broke the world]]. Ten-day weeks also appear at some point, though the first few books used seven-day weeks. There are also months, but most people ignore these and just go by seasons.
* Creator/UrsulaKLeGuin's works:
** The Literature/{{Hainish}} 'verse has scores of different calendars:
*** In ''Literature/TheLeftHandOfDarkness'', Gethenians count years backward and forward, with the current year always being year one. The more exact dates are determined by their relation to some historical events.
*** In ''Literature/PlanetOfExile'', Werel has a 400 days' lunar cycle and a solar cycle of 60 moonphases. Year, lifetime, what difference?
*** In ''Literature/RocannonsWorld'', Rokanan has years twice the length of an earth year (or, rather, the standard year used by the League of Worlds). Some regions use two twelve-month (or however many they have) cycles to make up a full year.
** Curiously, the fantasy book ''[[Literature/AnnalsOfTheWesternShore Gifts]]'' uses the Gregorian month names, but this might be a TranslationConvention, and it's not clear if it's meant to take place on an alternate Earth or another planet.
* ''Literature/PerdidoStreetStation'' and [[Literature/TheScar other]] [[Literature/IronCouncil works]] in the Literature/BasLagCycle use rather bold-faced names for the days, such as Skullday, Chainday, and Fishday.
** And this is only for the city of New Crobuzon, alone. In the floating city Armada, they have completely different names for months and days of the week.
* Creator/HBeamPiper's Terro-Human future history (e.g. ''Literature/LittleFuzzy'', ''Uller Uprising'') uses Atomic Era dating, starting the year zero A.E. at 2 December 1942 by the C.E. calendar (the date of the first self-sustaining nuclear chain reaction). Characters occasionally speak of Nth Century Pre-Atomic dates to refer to dates before that time.
* AustinTappanWright devised a fictional calendar for {{Islandia}}, which is explained in more detail in Basil Davenport's treatise on Islandian history. When Islandians found out about the Gregorian calendar, they liked the idea, but adapted the month names so they would have the right seasonal connotations for the SOUTHERN hemisphere. Thus, "Octen" and "Noven" are roughly the northern April and May.
* Creator/TerryPratchett: Most places on the Literature/{{Discworld}} use a 800-day calendar with eight-day weeks (the usual seven used in our world, plus Octeday). The year is divided into two half-years of thirteen months each (one month two weeks long, the other twelve four weeks long): Ick, Offle, February, March, April, May, June, Grune, August, Spune, Sektober, Ember, and December. This is because, due to the way the Discworld's sun works, seasons occur ''twice'' a year. The idea's also played with in ''Discworld/WyrdSisters'', which mentions several different calendars used by different countries and kingdoms, including one used by the Theocracy of Muntab, which counts ''down'' instead of up. No one's sure why, but most agree it's not a good idea to be around when it hits zero.
** It's usually only wizards and astronomers who think of a year as 800 days long. For them, the calendar year begins at the onset of the first winter (Hogswatch, which is the Discworld's Christmas). The start of the second winter to them is Crueltide. To the average Discworlder, concerned with practicalities like harvests and weather, a Disc "year" lasts for one turn of the seasons, which takes only 400 days. Crueltide to them is just another Hogswatch.
** Ankh-Morpork itself has restarted its calendar several times in its history, though dates are usually given in Unseen University's Ankh-Morpork Years. At least one of these restarts is a {{Retcon}} to make up for inconsistent dating.
** Years and centuries are often named rather than numbered on Discworld. Sometimes there's a reference to a year like "1784," but more often, years are referred to as "the Year of the Diffident Squid." And the whole continuity has just recently completed the Century of the Fruitbat.
** The reason for the hodgepodge of real and fictional month names appears to be that, as with so much on the Disc, Sir Terry gave months names based on what worked in that scene, and then Stephen Briggs came along later and worked out how it all fitted together.
* Creator/JRRTolkien's Legendarium (''Literature/TheLordOfTheRings'' etc) has several calendar systems for the different peoples. Used most commonly in ''[=LotR=]'', the Hobbits' Shire Reckoning uses a reformed calendar in which the week and the year are synchronized, and hides it behind a TranslationConvention. The Dwarves appear to use a different calendar, leading to such things as Gandalf in ''The Hobbit'' saying to Thorin "on the twenty-first of April, a hundred years ago last Thursday" when, in the Shire Reckoning, the twenty-first of April always falls on a Friday.
** Not only did the Hobbits and Dwarves have their own calendars, but so did Elves and Númenorean/Gondorean Men as well. The Númenorean calendar [[ShownTheirWork is based on the French Republican Calendar with names of the months translated into Elvish]].
* In Jack Vance's ''Literature/TheDemonPrinces'', the year zero corresponds to the year 2000 A.D. Therefore the first book taking place in 1524 means that it is really 3524 A.D.
** The fact that the new calendar began in 2000 A.D. is only given in a footnote.
** A foot note in the 4th book, written after Apollo XI, {{retcon}}s the epoch from 2000 A.D. to 1969 A.D.
* The "Common Era" in Creator/AlexeiPanshin's Anthony Villiers novels apparently is reckoned from the launching of Sputnik I in 1957.
* In ''Literature/ADeepnessInTheSky'' by Creator/VernorVinge, interstellar traders have done away with not just years and months, but also with days, hours and minutes. All timespans are measured in (appropriate powers-of-thousands of) seconds, with dates simply being the number of seconds since the UsefulNotes/{{UNIX}} epoch (with some unspecified [[ShownTheirWork but explicitly mentioned]] relativistic frame corrections) -- though in-universe [[FutureImperfect it is most commonly thought that the zero-second was at the first moon landing]]. Settled planets all have their own calendars. One way the traders know they have stayed too long is when they start using the locals' calendar.
* The ''Literature/HonorHarrington'' books count from 2103 AD (Gregorian) as 1 PD (post-Diaspora), the year that the first generation ship left Earth. The events of the books take place in the early 20th century PD (41st century AD). Planets set their years as "Year ''X'' AL (After Landing)", with days and months set as appropriate to planetary conditions. This means that a given planet will retain at least two calendars: The "Standard" (PD) year, & the "Local" (AL) year. The ones that are part of a multi-planet polity will track the capitol planet's year AL. Yay for computers.
** The religiously-founded planet Grayson averts this, using the Gregorian calendar even though it doesn't even remotely track with local conditions. For added confusion, the Graysons use the initials A.D. to mean Anno Domini, whereas in the rest of the universe A.D. stands for Ante Diaspora.
** The Kingdom of Manticore itself starts off with 5: Terran, Manticoran (the official one for the kingdom), Gryphon, Sphinxian (the latter two for their own seasons and days), and Medusan. Each additional planet that's added to the Kingdom adds another one.
** Nearly every mention of any amount of local years will be accompanied by "XX in T Years" (i.e. Terran years) to make sure we Earthlings have some frame of reference. Justified in this case: because of the kingdom's multiplicity of calendars, you'd expect to see them using a common frame of reference. Those people who have to deal with multiple planets and other nations (with their own calendar systems) are probably routinely doing conversions in their head automatically. You can see the same thing with people who use both metric and imperial measurements.
** Since Manticore is a merchant empire, it's extremely common for Manticorans to move to and from different planets, so local calendars are usually of little use to those new nomads. The series being MilitaryScienceFiction, it concentrates mainly on exactly this type of character, so the series generally dropped references to the local calendars and is now written mostly around the P.D. calendar.
* In ''Literature/TheGeneral'' series, dates on the planet Bellevue are calculated from "the Fall" of the interstellar Federation to which the planet once belonged.
* David Foster Wallace's ''Literature/InfiniteJest'' is set in [[TwentyMinutesIntoTheFuture a not-so-distant]] [[{{Eagleland}} version of America]] after the adoption of a calendar system that names each year after a corporate sponsor. Most of the book's plot takes place during the Year of the Depends Adult Undergarment. It's that kind of book.
* Creator/EdgarRiceBurroughs:
** In ''Literature/{{Pellucidar}}'', the immobility of the central sun prevents any sort of celestial timekeeping, leading the protagonists to proclaim (unconvincingly) that there is "no such thing as time" at the Earth's core. In fact, time in Pellucidar ''passes more swiftly for you when you're exerting yourself more''. At one point, the hero and his friend were separated and the hero had several weeks worth of adventures: fighting, running, lots of hard work. His friend merely strolled back to their lodgings, so only about an hour passed for him. It's a pity the "I'm not making this up" category has been disabled, because this nonsense ''deserves'' it.
** In ''Literature/JohnCarterOfMars'', it gets rather more rational treatment: he believes Dejah Thoris has died in "The Gods of Mars" because it has been a year -- but he has forgotten he's on Mars. The Martians have their own methods of counting time based around the "ord" (Martian year), analysed in detail in [[http://www.erbzine.com/mag16/1630.html this article]].
* Brian Caswell's ''Deucalion'' uses a metric time system of years AS (After Settlement), dating from first landfall on planet Deucalion (Earth still uses conventional time).
* In Melanie Rawn's ''[[Literature/SagaOfTheExiles Exile]]'' series, the year is divided into 36 10-day weeks, each with a name and a patron saint, plus a handful of feast days for a total of 366 days. This replaced a system where every day had it's own patron saint. Needless to say, this particular setting has a lot of saints.
* The ''Literature/{{Dragonlance}}'' series. There are seven days each week and twelve months each year. But each day and month have eight different names, each from a different culture. The titles of the Chronicles trilogy, in the Gregorian calendar instead of elven are: ''Dragons of October'', ''Dragons of January'', and ''Dragons of March''. The War of the Lance lasts less than a full year. [[AndKnowingIsHalfTheBattle And now you know.]]
* In Creator/StephenKing's ''Franchise/TheDarkTower'', Roland's world uses different names for the months.
* On Literature/{{Gor}} each city-state has its own calendar, counting Year X of City Administrator Y's reign or some other locally-important event. To standardize, most city-states also count in years C.A. - Contasta Ar, "from the founding of Ar," the largest city-state. Actual book quote:
-->Chronology is the despair of scholars on Gor.
* ''Literature/TheReynardCycle'': Though no dates are ever mentioned (leading to much fan speculation about exactly when and where the story is taking place), the months of the year have names like Pearlmonth, Bloodmonth, Reaping, etc.
* In ''Literature/StarTrekDepartmentOfTemporalInvestigations'', alongside multiple human calendars including Christian, Islamic, Hindu and Mayan examples, the chapter headings include dating systems from many Star Trek cultures, including Vulcan, Andorian, Cardassian, Klingon, Deltan, Tandaran and Risian. Most of these alien calendars have been plotted out in full by the author in his annotations. Other Franchise/StarTrekNovelVerse books have given dates in mostly consistent Klingon, Vulcan, Romulan and Andorian calendars, but this is probably the first time the entire calendar has been plotted for so many races.
* Franchise/{{The Witcher}}world knows at least two calendars, human and elven. The world's actual year length appears to be used by the human calendar, while elven year's length appears to be some two thirds of it. Both share equinoxes and solstices as points of reference.
* ''Literature/ASongOfIceAndFire'' is set in the second to third century after Aegon's Landing. The seasons are random in length, but are much longer than the years, making it uncertain what a "year" actually means.
** Probably related to a complete rotation of the sun, our own calendar is measured as such, rather than the passing of seasons.
** ''Literature/TheWorldOfIceAndFire'' clarifies an in-universe misconception -- namely, that the Westerosi calendar doesn't actually begin at Aegon's Landing and the ''start'' of his Conquest, but the date when he was officially crowned as King of Westeros at the ''end'' of the Conquest, which was a couple of years later.
* The various chapters of ''Literature/OutOfTheDark'' provide the date in both the Gregorian and the galactic standard calendar. The epilogue introduces a third calendar, replacing the Hegemony's calendar with the notation [[spoiler: "Year 1 of the Terran Empire"]].
* The ''Literature/{{Animorphs}}'' {{prequel}} ''The Hork-Bajir Chronicles" gives Earth dates (the late 60s), Andalite dates (a year in the 8000s with decimals attached), Hork-Bajir dates (simply a reference to the current season) and Yeerk dates (a reference to generational cycles).
* In ''Literature/TheKingkillerChronicle'', a week is called a "span" and has eleven days. It's unknown how many spans there are to a month, nor months to a year.
* ''Literature/TheHourBeforeMorning'' has years reckoned up from the beginning of the dominant empire -- more than two thousand of them, and an uncertain period between that and the time Earth passed into legend.
* ''Literature/WarriorCats'' uses the "moons" type, having the cat characters measure things in lunar cycles. They also have different names for the seasons. (Leaf-bare for Winter, Newleaf for Spring, Greenleaf for Summer, and Leaf-fall for Autumn/Fall.)
* In Claire Winger Harris's short story "The Fate of the ''Poseidonia''", Earth's calendar has been simplified to have 13 months of 28 days, plus a New Year's Day that's separate from any month.
* Human scholars in the ''Literature/GarrettPI'' series use the dwarven dating system, because humans' own calendars tend to change too often as monarchs re-start their kingdoms' year count from their own births or coronations.
* The ''Literature/ReflectionsOfEterna'' series is set in a ConstructedWorld that uses a calendar based on 400 years-long Ages, each associated with one of the four elements (four being the ArcNumber of the series): the Age of the Waves follows the Age of the Lightning, followed by the Age of the Rocks, the Age of the Wind, and then Lightning again, in a cycle. Historically, each EndOfAnAge, called "Fissure" in-universe, has been accompanied by massive political and social upheavals: for instance, the last time it occurred (the Rocks succeeded the Waves), the millenia-old empire of Taligoia was taken over and rebuilt from scratch into the kingdom of Talig by a charismatic usurper. The series itself opens in the year 399 of the Age of the Rocks, soon to be replaced by the Wind--and there are SignsOfTheEndTimes all over the place this time around.
* ''When the Blue Shift Comes'' by Creator/RobertSilverberg is set in "Year 777 of Cycle 888 of the 1,111th Encompassment of the Ninth Mandala" ... a fact which the LemonyNarrator cheerfully points out conveys absolutely nothing to the reader beyond being so far in the future that all our calendars have been forgotten.
* ''Literature/SholanAlliance'': [[JustifiedTrope Justified]] in that Shola's year is several days longer than Earth's 8766 hour orbit.
* ''Literature/TheStormlightArchive'': Roshar has a calendar based around the [[HostileWeather highstorms]], since seasons are random and only last a couple weeks at a time. Each year is five hundred days, with the end of the year marked with "the Weeping," two weeks of constant light rainfall and no highstorms except for one right in the middle--though every other year is a Light Year, with no highstorm in the middle of it. Together, each pair of years creates the thousand day cycle of storms which influences everything. This does mean that the characters are older than their stated ages. However, Rosharan days are also shorter than Earth days, so in the end a single Rosharan year is only ten percent longer than an Earth one.
* ''Franchise/StarWarsLegends'' counts dates as "BBY" and "ABY", Before and After the Battle of Yavin, where the first Death Star was destroyed. Mention is occasionally made of the old Imperial Calendar that was used by the Empire. At one point Luke, doing some historical research, expresses exasperation at each new regime feeling the need to implement a new calendar, which makes pinning down dates more difficult. As for the months, originally the setting used a 10-month calendar where each month had 35 days, with three 5-day festival weeks and three other holidays added to give 368 days. However, in a few later works a 12-month system was retconned in. Some works have a Galactic Standard Calendar based on Coruscant's (the capital of the Republic and later Empire), which had multiple variants, and may account for the discrepancies.
** Some planets and systems also use their own calendars, Wookiepedia lists about ten or so.
* The nations of Euterpe in Creator/TeresaEdgerton's ''Goblin Moon'' use a calendar of nine forty-day "seasons", rather than months. The actual solar year is a bit longer than that, so celebratory "intercalary days" round it out every three seasons.
* ''Literature/TheMachineriesOfEmpire'' features AppliedPhlebotinum that depends, among other things, on lots of people following the same calendar and believing the same things. Entire wars are fought over preventing (or creating) "calendrical rot."
* Literature/TheTowersOfFebruari: In the alternate world Tim winds up in, the months have the same names as in our world, but they all are 30 days long, and there are 5 unnamed days at the end of the year. The first clue he gets that he's in a strange place, is that when he asks someone "What day is it today?", they answer "30 February".

[[folder:Live Action TV]]
* Though the original calendar system is not explained, ''Series/BattlestarGalactica2003'' makes reference to a (new) calendar system after the exodus from New Caprica. After passing a guilty sentence on a Cylon collaborator, the date is stated as the "third day of the Second Exodus."
* ''Series/{{Caprica}}'' introduces a twelve-month calendar using the same names as the Roman calendar: Ianuarius, Februarius, Martius, Aprilis, Maius, Iunius, Quintilis, Sextilis, September, October, November and December. The Roman months Quintilis and Sextilis were renamed after Julius Caesar and Augustus Caesar respectively.
* In the ''Series/DoctorWho'' episode "The End Of The World", the Doctor claims that the year to which they've traveled is "5.5/apple/26, five billion years in your future".
* The ''Series/RedDwarf'' episode ''Better Than Life'' had a newsreader announce the news for Friday the 27th of Geldof.
* ''Franchise/StarTrek'''s famous stardates, though these are much more complex than most. They also use straight-up AD/BC.
** The writers of ''Series/StarTrekTheOriginalSeries'' made up stardates as they went along without any sort of linear progression or continuity. Early fans who tried to use them to reconcile episodes' production order and air date order tended to end up as inmates at Tantalus Colony. When an interviewer asked James Doohan how stardates worked, Doohan replied (paraphrasing), "Sorry, even Scotty couldn't figure that out." The writers guide for the series attempts to HandWave these discrepancies by claiming "Stardates are a mathematical formula which varies depending on location in the galaxy, velocity of travel, and other factors, can vary widely from episode to episode."
** Parodied in ''WesternAnimation/{{Futurama}}'':
--->'''Zapp:''' Captain's journal. Stardate: uhhh...\\
'''Kif:''' (''sighs'') April 13.\\
'''Zapp:''' April 13... point two.
** Averted in ''Enterprise'', which still used the Gregorian calendar; the series predates the founding of the Federation which would in turn adopt the Stardate.
** Also averted in the new ''Star Trek'' movie which uses stardates that are just different ways of saying the date than we use now. Stardate 2248.42, for example, would be February 11th (the 42nd day of the year), 2248 AD.
** For the three "middle children" of the series (''Series/StarTrekTheNextGeneration'', ''[[Series/StarTrekDeepSpaceNine Deep Space Nine]]'', and ''[[Series/StarTrekVoyager Voyager]]''), the stardates have some coherency. They range from the 41000s for TNG's first season to the 54000s for the last season of ''Voyager''. Originally, the 4 stood for the 24th century, the 1 stood for the first season, and the last three numbers were given out linearly to the episodes of a season, with the digit after the period representing a fraction of days. ''Deep Space Nine'' started during TNG's run and used similar stardates, so the 4 had to lose its "24th century" meaning and the second number lost its season meaning, leaving a seemingly coherent in-universe system: a thousand stardate units equal a year. ''Voyager'' continued this, and so did the TNG movies. While this may seem like it makes sense, there are countless contradictions, errors, and inconsistencies.
*** Notably, this system would place Stardate 0.0 at 1st January 2323 AD... some thirty years ''after'' the events of ''[[Film/StarTrekVITheUndiscoveredCountry Star Trek VI]]''. Which isn't necessarily a problem, if the Federation changed the Stardate system at some point along the way, like what we know they did with the warp speed scale.
** The ''[[Series/StarTrekDeepSpaceNine Deep Space Nine]]'' episode "Soldiers of the Empire" reveals that Klingons use a stardate system of their own (day in the year of Kahless). Kahless was the founding figure of their civilization, so it makes perfect sense to them.
* ''{{Series/Andromeda}}'' has one calendar system but several reckonings. The base calendar is the Commonwealth Year (CY). It's reckoning is the founding of the Vedran Empire (the precursor to the Systems Commonwealth), nearly 10,000 years ago, when it was known as the Coronation Year. Dates before the founding are described as Before the Imperial Era (BIE). There is a point of correlation: the English translation of ''Thus Spake Zarathustra'' (AD 1891 = CY 6811), and it has been stated by WordOfGod that Vedran years were roughly equal to those on Earth. Then you have the most recent calendar, AFC (After the Fall of the Commonwealth), which has only run for about 300 years (AFC 1 = CY 9787).
* The video compilation "VIDEO VICTIM" includes a skit where Japanese comedy duo Rahmens introduces us to [[https://www.youtube.com/watch?v=FttcMVlm_oQ the new world calendar]].
* ''{{Series/Killjoys}}'': The year is apparently "1062", without any explanation as yet of what the starting point was.

* ''Music/YearZero'' by Music/NineInchNails. The story takes place in the United States in the year 2022; or "Year 0" according to the American government, being the year that America was reborn.

[[folder: Play-by-Post [=RPG=]s]]
* In Roleplay/{{Shadowside}}, the world switched over from 2007 AD to 00 AED, "Years After Evos Dawn".

[[folder: {{Radio}}]]
* ''Radio/TheBurkissWay'''s parody of ''Literature/NineteenEightyFour'' begins on Scargillday 14 Vanessagust[[note]]Referencing militant miners' union boss Arthur Scargill and left-wing actress/activist Vanessa Redgrave[[/note]].

[[folder:Tabletop Games]]
* The world of Dominaria in ''TabletopGame/MagicTheGathering'' has an undefined calendar within the year, though years are given in several different scales. A nation famed for its education and archaeologists is even referenced in the name of the most well-known calendar -- Argivian Reckoning (AR), which places Year 1 on the year Urza and Mishra, leaders of the two sides of the Brothers' War, were born.
* The biggest ''Dungeons and Dragons'' campaign settings include some form of alternate calendar. [[http://www.omnimulti.com/other/chrono.html This converter contains most of them.]]
** The ''[[TabletopGame/{{Greyhawk}} World of Greyhawk]]'' Calendar is one of the most well known, even having a [[http://en.wikipedia.org/wiki/Greyhawk_Calendar Wikipedia article]] covering it. A year on Oerth is precisely 364 days long with no leap years, due to the "Greyspace" solar system actually being a geocentric system. The calendar year is split into twelve months of 28-days each and four 7-day festivals, which are every three months. Due to this, each weekday always falls on the same day every year. The months follow the lunar cycle of Luna, with the festival weeks following the lunar cycle of Celene.
** The ''TabletopGame/ForgottenRealms'' setting [[http://forgottenrealms.wikia.com/wiki/Marking_the_Years was hit with it rather hard]]. The main calendar on Faerun is Dale Reckoning (DR), aka Freeman's Reckoning (FR). Present Reckoning (PR) is zeroed at the Time of Troubles. The Roll of Years names years (i.e. "Year of Rogue Dragons") according to the prophecies of the seers Augathra and later Alaundo covering -422 DR to 2163 DR -- which at least helps to stitch local numerical calendars together. There are even different versions of this, where the orcs started out the year in a blaze of conquest and by the end of the year had been kicked back into their holes once they'd pissed enough people off. They call that "The Year We Went Too Far". The Forgotten Realms also uses a ten day week (called, appropriately enough, a tenday) and several feast days, holidays, and other events that vary from nation to nation throughout the year.
** On ''TabletopGame/{{Eberron}}'' a year consists of twelve months (each named after one of the twelve moons) and a week of seven days, seeming like they just came up with with fancy new names for the months and and days to seem exotic, however the months are only 28 days each, making all characters a couple of years younger in real time than they seem. Interestingly (or not, depending) there was originally one more moon, implying before the appropriate cataclysm the year and lunar cycle used to be much closer to Earth's.
** A year on the planet ''TabletopGame/{{Mystara}}'' is 336 days long, allowing for a handy calendar of twelve 28-day months. There is no distinction between the lunar and solar calendars, as new or full moons always fall on the same dates in each year. Each country has its own names for the 12 months; the chief exception is that of the shadow elves, whose year consists of 24-day months, each named for one of their religion's 14 Verses. (Being subterranean, these elves don't need to synch their calendar with celestial events, and keep track of dates only to schedule their religious ceremonies.) ''Inside'' Mystara, the Hollow World's stationary inner sun doesn't provide for conventional day/night or seasonal cycles. Rather, dates are tracked by the orbits of the major flying continents.
** On Athas, the world of ''TabletopGame/DarkSun'', the calendar system is a merchant's calendar that is used by all of the known Merchant Houses to help with trade, which is based primarily on the orbits of the two moons, Ral (11-years to return to the same orbit) and Guthay (7-years to return to the same orbit) which each year for each moon designates a certain word used to define the year (Tyr's Free Year 1 is the 4th year for Ral, designated "Priest", while it is the 5th year for Guthay, designated "Defiance", so it is the Year of the Priest's Defiance). The calendar year is typically broken into 15 months comprised of 5 weeks each 6 days long (30-day months). A rather complex calendar system overall. The actual year numbering is either based on the King's Ages (older system), or since Tyr's revolt (Free Years).
** In ''Literature/{{Dragonlance}}'' people started numbering up from zero after the Cataclysm, so the abbreviation was A.C., anything before the Cataclysm was labeled P.C., and after what is sometimes called the Second Cataclysm in ''Dragons of Summer Flame'', S.C. was used for a while, but was later dropped in official supplements and novels, going back to using A.C.
** Subverted in ''TabletopGame/{{Ravenloft}}'', where the calendar works like Earth's, despite the setting's having been [[PatchworkMap cobbled together]] from bits and pieces stolen/copied from other worlds. The Barovian calendar predominates for the numbering of years, while the names of months would seem to have been imported from Mordent.
** In ''TabletopGame/{{Planescape}}'', there's no real seasons, as each plane has different physical laws. Weeks have seven days, and years have 12 months, but their names reflect the calendar of whoever is keeping track. In Sigil, years are often measured by the year an influential Factol has held his position, usually the Factol of the Guvners (seeing as they're in charge of keeping the records.)
* In ''TabletopGame/{{Warhammer 40000}}'', the Imperium ''still'' uses the Gregorian calendar, but the presentation of years is different: the current year as of this entry in the Gregorian calendar, 2008, would be written as "008.M3". However, the internal workings of the calendar is a bit different than the modern Gregorian Calendar. Take for example December 24th 2008: the using the Imperial dating system, this would be 0979008.M3 . The first number (0) means that the dated event took place in the Sol system, allowing perfectly accurate dating. The more inaccurate that dating becomes, due to distance from Earth and lack of information, the higher the first number will be. The next three ciphers (979) the fraction of the year that has passed[[note]]though this is only really used in bureaucratic records[[/note]]. The next three ciphers (008) is the year. And the ending (.M3) is the millennium.
* ''TabletopGame/{{Exalted}}'' uses a dating system starting with the founding of the (second) Realm, and has a rather different calendar inside each year also. The year is divided into 15 months (ascending, resplendent, and descending Element, where Element is one of Air, Earth, Fire, Water, Wood (not in that order)), plus five days of Calibration, when spirits are at their strongest and the gods are all partying.
** Well if you are going to pedantic about it (and I am) Calibration is not part of the year, the five days of calibration do not belong to either the year before or the year after.
** The various different regimes use different calendars, many of which will be in use at the same time in different places. The nominal "start of game" year would therefore be Realm Year 768; 4878 Dawn of Autochthonia; Year 4999 of Our Everlasting Glory and the Year of the Mouse in the Bronze Era of the 11th Epoch the Dragon-Blooded Shogunate.
** Being ''Exalted'', it also has an ''extremely'' alternative calendar -- the Calendar of Setesh, which not only tracks time in the Underworld, it actually cements the concept of time passing in a linear fashion down there.
** An interesting detail is that despite having 425 days, each of 25 hours, in the year, a sixteen-year-old in Creation is functionally equivalent to a sixteen-year-old on Earth.
* The German P&P System ''Das schwarze Auge'' (''TabletopGame/TheDarkEye'' in the US) has several calendar systems. The most common (at least in the Middlerealm) is one that uses a year of 365 days with 12 months of 30 days each, named after the Twelvegods (Praios, Rondra, Efferd, Travia, Boron, Hesinde, Firun, Tsa, Phex, Peraine, Ingerimm and Rahja). The five days after Rahja are called "Nameless Days" and are dedicated to the Nameless God (you better stay at home during those!). The year 0 can be either the fall of the city Bosparan, the year Emperor Hal (or Reto) ascended to the throne, etc. And that's only for those believing in the Twelvegods.
** [[FantasyCounterpartCulture There is only one god and His name is Rastullah.]]
** Everybody (besides the disciples of Rastullah above) uses the calendar of the Middlerealm, just with other names for the months. And even the disciples of the Onegod observe the Nameless Days.
** And that's just the human side of things. Orcs count years of 240 months, 28 days each, Achaz (lizardmen) have weeks of 5 days and months of 33 days, and so on.
* Averted in ''TabletopGame/BattleTech'' where thousands of planets all still use the current AD system. The main universe storyline runs from 3020 to 3135. Individual planets have 24 'hour' days (where an hour can be as little as 30 minutes on some fast-spinning planets) based on their own rotation, and years based on their own orbital path. But Human civilization as a whole maintains the earth-based AD Calendar, with 0 hour based on Greenwich Mean Time, including leap years!
* In ''TabletopGame/{{Talislanta}}'', a calendar year consists of seven months, each month lasting for seven weeks of seven days. Talislanta has seven moons, so it makes a certain degree of sense.
* In ''TabletopGame/{{Paranoia}}'', the days of the week are as follows: Oneday, Twosday, Threeday, Fourday, Fiveday, Sixday, and [[TheLastOfTheseIsNotLikeTheOthers Mandatory Inspection Day]].
** And the year is 214. See, The Computer decided that 214 makes things sound nicely established but not too old, so the year is ''always'' 214.
* The ''TabletopGame/IronKingdoms'' use a calendar where 7 days make a week, 4 weeks make a month, and there are 13 months per year. Furthermore, the days are not named, but the weeks are, and the whole thing is based around the cycles of the planet's 3 moons. Every 3 years, all 3 moons are new on the same night, which makes an extra day on the calendar. This 'Leap Day' is celebrated in a festival called The Longest Night.
* In ''TabletopGame/WarhammerFantasyRolePlay'', Imperial calendar counts the years from the coronation of Sigmar, an event marking the birth of the Empire (canonically the game is set in 26th century). The year is 400 days long and divided into 12 months with six with intercalary holidays, while weeks are eight days long. Other nations use similar calendars, usually numbering the years from the founding of respective state (e.g. 977 IC for Bretonnia, 1524 IC for Kislev). And the calendar of High Elves is divided into epochs of variable length, each one referring to the reign of the particular Phoenix King (very similar to the Japanese eras). Wood Elves, Ungols and other nomadic tribes use various lunisolar calendars.
* ''TabletopGame/SeventhSea'' has a calendar that, like everything in ''7th Sea'', is strongly reminiscent of the one used in 18th century Europe with just enough cosmetic changes to make it more of an {{Expy}} that a direct reproduction of the real world.
* In ''TabletopGame/{{Traveller}}'' the calendar of the Third Imperium starts at the beginning of the reign of [[FounderOfTheKingdom Cleon]] [[MagnificentBastard the]] [[GalacticConqueror Great]]. Notably, the founding year was designated as Year Zero, and years are generally just expressed as a (possibly negative) number. (1 AD is Imperial year -4520.) The official calendar has 365 days, numbered 001 to 365. Day 001 is a holiday; the other days are arranged in 7-day weeks, with weekdays Wonday, Tuday, Thirday, Forday, Fiday, Sixday, and Senday. There is an official Imperial Office of Calendar Compliance to insure that this calendar is kept up between worlds. Some have said that this doubles as a SecretPolice.
** The Solomani Confederation, even though they no longer control Terra, [[AvertedTrope still use the Gregorian calendar]], as do a few other groups like the Sword Worlds. Notably, because of leap days, their year and the Imperial year have gotten out of synch by most of a year.
* Some places in ''{{TabletopGame/Rifts}}'' use the Gregorian Calendar, but in North America, the Post-Apocalypse (P.A.) calendar is used. It was established by the Coalition States capitol of Chi-Town some 200 years AfterTheEnd, and 1 P.A. is the founding of the city. It is used to mark the end of the Second Dark Age, when Humankind began to rebuild civilization. The first book was set in the year 101 P.A, and subsequent {{Sourcebook}}s advanced the timeline to 109 P.A, which is 2395 A.D. Gregorian. Months and days appear to be unchanged. Hell, the fluff implies that the Coalition still celebrates Christmas.

[[folder:Video Games]]
* An in-game book in ''VideoGame/DungeonSiege'' hints at this; a guard's journal features such 30-day months as "Threb", "Smoth", and "Foth".
* ''Franchise/TheElderScrolls'' games have a system which is actually our own calendar system, but with different names for the months and days of the week. October becomes "Frostfall", Saturday becomes "Loredas", and so forth. The number of the year is determined by the amount of time since the beginning of that particular Era. ''[[VideoGame/TheElderScrollsIVOblivion Oblivion]]'' begins on the 27th of Last Seed (August) in the 433rd year of the Third Era, which began with the unification of Tamriel and founding of the Septim Dynasty and ended with the events of the game. ''[[VideoGame/TheElderScrollsVSkyrim Skyrim]]'' begins on the 17th of Last Seed in the 201st year of the Fourth Era, which began following the conclusion of the Oblivion crisis.
* ''VideoGame/FinalFantasyTactics'' uses a calendar based on the Western Zodiac. This was changed in the English PSX version to the Gregorian calendar, but kept in the PSP version.
** ''VideoGame/FinalFantasyTacticsA2'' has its own calendar, which is the regular one but with different names and twenty days for every month.
* ''VideoGame/FinalFantasyVII'' uses Gregorian names for months, but February has at least 30 days. And the number of the year gets reset after each 2000-year Greek-letter "era", so 1999 of the Mu era was followed by 0000 of the Nu era.
* ''VideoGame/{{Freelancer}}'' measures the years as "B.S." ("before settlement") and "A.S." ("after settlement"), with the arrival of the Liberty to Planet Manhattan as its zero point; days and months, meanwhile, are measured with our Gregorian calendar and our 24 hour days. In the popular Discovery modification, the calendar in House Gallia uses AGS, or After Gallic Settlement.
* The ''Ogre'' series has the Zeteginean calendar, which corresponds to the Gregorian one for the purposes of allowing the player to choose a birthday, but is otherwise different.
* ''VideoGame/GuildWars'' has its own set of calendars, one for the Canthan continent, and one that is shared by both the Tyrians and Elonans. The Elonan calendar also has a zero year some two centuries before the Tyrian calendar.
* The freeware space exploration game ''VideoGame/{{Noctis}}'' puts the player in control of a cat-like alien creature called a Felysian, and employs the calendar of his civilization. For example the base unit, called ''epoc'', corresponds to about 32 human years, but the smallest unit, the ''triad dexter'' (a billionth of an ''epoc'') is "incidentally" equal to a second.
* ''VideoGame/KingdomOfLoathing'' uses a 12-month calendar in which each month has 8 days. The first day of each month is when Ronald, one of the Kingdom's two moons, is full. The holidays that affect the goings-on of [=KoL=] are: [=KoL=]-specific holidays, which pop up only on their day of the [=KoL=] year; real-world holidays and other observances, which occur when they occur in our year (for example, our Friday the 13th causes things to happen there, even though [=KoL=] months don't have that many days to begin with); and parody holidays, which tend to happen ''both'' on a specific date on the [=KoL=] calendar ''and'' on the date of the parodied observance.
** This occasionally creates interesting scenarios where real holidays and their ingame versions intersect, including one memorable instance where Christmas (or [[YouMeanXmas Crimbo, as it's known in game]]) and the in-game Halloween coincided, or ''Drunksgiving'', where the in-game holiday 'Feast of Boris' occurred on the real-life St. Patrick's Day.
* In the MMORPG ''VideoGame/EveOnline'', one of the EVE chronicles discusses how the four empires decided on a common calendar system. They ended up using the Gregorian calendar, and the date of the decision became January 1, year 0. The months of the EVE calendar match up with those in real life. Years are done a little differently; the year of the game's launch, 2003, corresponds with the in-game year 105. 2008 is referred to in-game as year 110.
** Averted in the Amarr Empire, where they still count from Anno Domini (As of 2009, the current in-game year is 23347 AD and 111 YC). Also, it seems reasonable to assume that the other empires have their own calendars. One has been mentioned for the Gallente Federation - The Age of Rouvenor (AR), with Year 0 established when king Doule Dos Rouvenor III rose to power in 21714 AD.
* In the ''VideoGame/StarCraft'' expansion, the United Earth Directorate uses a different calendar, and the present year, 2501 AD (The original game used the Gregorian calendar), is marked as 872 GD. It's not explained what significance the year 1629 AD has to be year 0 on the UED calendar.
** It was the year the dutch astronomer Christiaan Huygens was born: given his contributions to the fields of mathematics and astronomy, and the fact that he was one of the first to speculate about the existence of extraterrestrials, it may be viewed as a starting date as good as another, given the kind of universe that is Starcraft.
*** Seeing as how the UED was formed out of the UPL due to the discovery of aliens in the koprulu sector, it would seem that they chose the date because of Christiaan Huygens speculations on extraterrestrials. Which would make for the fun realization that this calendar is fairly new, as aliens had only been discovered several months before the UED invasion.
* ''VideoGame/{{Syndicate}}'' gave it's dates in N.C., simply standing for New Calendar. This added somewhat to the corporate dystopian feel of the game.
* Dates in the two pre-Wii ''VideoGame/PaperMario'' games are written with [[YearX triangles and circles and stuff]] instead of names ''or'' numbers.
* The ''VideoGame/HarvestMoon'' games use years made up of four thirty-day seasons. The years themselves count up from the start of the game, which is usually when the player character arrives in town. The ''VideoGame/RuneFactory'' spinoff series takes this one step further by combining Saturday and Sunday into "Holiday", meaning that every day of the year will always be on the same day of the week.
** In the ''Wonderful Life'' games, there are still four seasons, but only ''ten'' days per season (with no designation for days of the week).
** Averted in ''[[VideoGame/HarvestMoonMyLittleShop My Little Shop]]'', which, like ''VideoGame/AnimalCrossing'', uses your Wii's system calendar.
** ''VideoGame/StardewValley'', which takes inspiration from ''Harvest Moon'', uses 28-day seasons. While it does achieve the "years with identical week structures" effect that ''Rune Factory'' does without shortening the week, it also means that each year is 8 days shorter than in those two games.
* ''VideoGame/{{Homeworld}}'' uses ''four'' calendars: Kharakian Dating System (KDS), Before Hiigaran Landfall (BHL), After Hiigaran Landfall (AHL), and Galactic Standard Year (GSY). The first three were used exclusively by the Hiigarans, while GSY, as implied by its name, is used by all other races. BHL and AHL are used in the same manner as our BC and AD, except for the use of year 0. KDS started in 1216 BHL, while GSY began in 9510 BHL. Confused yet? If so, then I would not even attempt to read [[http://homeworld.wikia.com/wiki/Homeworld_universe_timeline this timeline]].
** Strangely enough (or, more likely, so as not to confuse the players even more), all four calendars have the same length of the year.
* ''VideoGame/SuperRobotWars'' counts, since it has ''Franchise/{{Gundam}}''. Here are a few examples
** ''VideoGame/SuperRobotWarsAlpha'' series takes place in the New Western Calendar
** ''VideoGame/SuperRobotWarsCompact'', ''VideoGame/SuperRobotWarsCompact2'' and ''VideoGame/SuperRobotWarsCompact3'' takes place in 00XX
** ''VideoGame/SuperRobotWarsDestiny'' takes place on Space Year 145
** ''VideoGame/SuperRobotWarsJudgment'' takes place on [[Anime/MobileSuitGundamSeed Cosmic Era year 70]]
* The ''Franchise/DragonAge'' universe actually has multiple calendars. The most widely-used one is the Chantry calendar, which groups time into 100-years Ages, and which starts with the founding of the Chantry. In the year before a new age is set to begin, the Chantry look for portents to determine the name of the upcoming age, with the name reflecting major events that will happen during those hundred years. The title actually comes from the Chantry calendar (they declared the present age the [[TitleDrop Dragon Age]]). Events prior to the Chantry are said to be in the Ancient Age, with the year given ''in negative''. The Tevinter Imperium has its own calendar that starts with its founding, and the elves have their own calendar that begins with the founding of Arlathan. [[http://dragonage.wikia.com/wiki/Ages See here for more info.]]
* ''VideoGame/SoulNomadAndTheWorldEaters'' uses the Tamaito calendar, with the game taking place in the year 800.
* In both ''VideoGame/{{Xenogears}}'' and ''VideoGame/{{Xenosaga}}'', humanity switches to the "Transcend Christ" calendar, with AD 2510 as TC 1. It is Gregorian apart from the new reckoning, which is the beginning of humanity's building ships to leave Earth and explore the stars.
* ''[[VideoGame/EscapeVelocity EV Nova]]'' years use the suffix "NC", for "New Calendar". The game starts in 1177 NC; 0 NC was 2780 AD, the year FTL inventor Omata Kane died.
* In the ''[[VideoGame/{{X}} X-Universe]]'', year 0 Argon Stardate is 2170 AD, twenty-four years after a Terran warfleet lured [[AIIsACrapshoot insane terraforming drones]] away from Earth, trapping themselves and the terraformers in the X-Universe. The fleet established their own society (called the Argon, after their leader Nathan R. Gunne), and erased all mention of Earth from their histories to prevent people from inadvertently leading the terraformers ''back'' to Earth. The games take place over 700 years later.
** The Terrans still use Earth's calendar, understandably.
* ''VideoGame/DwarfFortress'' has a variation on the Gregorian calendar, although with the names of minerals for the months.
* In ''VideoGame/SidMeiersAlphaCentauri'', a subversion: The game begins in AD 2101 and you presumably continue to follow the Gregorian calendar, but for whatever reason you now them "Mission Years" (MY). One imagines that this is rather confusing to anyone on Planet who cares to think about it.
* ''VideoGame/EverQuestII'' takes place in the year 500 A.K. (After Kerafyrm) starting the new calendar after the famous day when the powerfully insane dragon was woken up by mortals and went on a rampage against his own dragon-kind in the original ''VideoGame/EverQuest''. Things get complicated when you try to compare it to the calender that the first game used: There was none. Each server had it's own in-game date, and always fluctuated during downtimes like patches and such. However, it doesn't stop there. During those 500 years between the two games, the Ogres rose up and built a new empire that tried to take over the world. Their own records of the 2nd Rallosian War are recorded in their own established calendar system. Over on the continent of Kunark, the evil {{Lich}} Venril Sathir built a new Sathirian Empire, using the ancient Sathirian Calendar themselves. None of these established calendars have any overlapping date of reference to pinpoint exactly when they take place on a universal calendar that the player can reference. This was done intentionally by the developers so they would have some leeway to fit in new events that happened during the 500 year period without conflicting with anything.
* The ''VideoGame/{{Metroid}}'' series uses [[{{Microts}} "cycles" and subdivisions thereof]] for its calendar system. The only point of reference given is that [[TheFederation the Galactic Federation]] officially formed in 2003 CC (Cosmo Calendar). What relationship, if any, the Cosmo Calendar might have to our own is never even hinted at.
* ''[[VideoGame/{{Touhou}} Touhou Project]]'', according to ''[[AllThereInTheManual Curiosities of Lotus Asia]]'', has two calendars: the official Gensokyo calendar that measures years as "seasons", starting from 1885 when the Hakurei Barrier was created, which uses the plain ol' Gregorian calendar but with traditional Japanese names (April, May and June, for example, become "Uzuki", "Satsuki" and "Minazuki"). There is also an unspecified {{youkai}} calendar, adjusted to natural phenomena like earthquakes or the blooming of bamboo flowers, which takes into account the youkai's extended lifespans, but few youkai actually use it.
* In ''VideoGame/HalfMinuteHero'', the 1st year of the Goddess Era marked the first time the Time Goddess descended upon humans. Every game mode takes place at a different point in the Goddess Era.
* In ''VideoGame/{{Civilization}} V'', the Mayans use their own calender, instead of the Gregorian calendar everybody else uses, upon discovering Theology. They also get a free Great Person every baktun, so this isn't a merely decorative effect.
* The MSX ''VideoGame/{{Gradius}}'' series (a.k.a. the ''[[MarketBasedTitle Nemesis]]'' trilogy) uses Gradian years, a calendar system which no other entries of the series used at the time. The original ''Gradius'' is set in the Gradian Year 6658, which is followed by ''Gradius 2'' (aka ''Nemesis 2'') in the Gradian year [[NumberOfTheBeast 6666]] and ''Gofer no Yabou Episode 2'' (aka ''Nemesis 3: The Eve of Destruction'') in 6809. The MSX version of ''VideoGame/{{Salamander}}'' is also part of this chronology, being set in the Gradian Year 6709. This calendar system would later be implemented into the mainline series with ''Gradius V'', which is set in Gradian Year 8010. The Wiiware game ''Gradius Rebirth'' is a prequel to the MSX ''Gradius 2'', being set in Gradian Year 6664.
* ''VideoGame/ImperiumNova'' uses a 400-day calendar with ten months to keep things simple. Each galaxy numbers years based on the ascendance of the current Imperial house, which like the Japanese system can make long term dating difficult in certain galaxies.
* In the video game [[VideoGame/{{Siren}} Siren 2]] the player can locate a calendar and other materials dated using the Japanese imperial system that begins a new count from the first year of a new emperor's reign. Strangely, all the documents use the "Showa" era, which ended in 1989 (Showa 64) even though some of the game takes place in "present day" 2008 (which in this case would be Showa 83). This should be the "Heisei" era, implying that the game takes place in a world where Emperor Hirohito ruled for at least another 20 years later than in reality.
* [[AllThereInTheManual Officially]], the year the Arcade game ''VideoGame/{{Strider}}'' is set (2048 A.D., as seen in the first stage's intro) was [[MeaningfulRename rebranded]] by the title's BigBad as "Meio Year One", signaling the beginning of his rule. This was given a nod in the 2014 reboot, which is set in the year "Meio 0048", implying the game happens roughly half a century after Grandmaster Meio took over the world.
* The D'ni calendar from the ''VideoGame/{{Myst}}'' franchise divides its year (''hahr'') into ten ''valleetee'' (~months) of 29 ''yahrtee'' (~days). As the D'ni civilization lived underground and on other Ages will disparate day/night cycles, they had little cause to align their calendar with surface-world days or lunar cycles. Note that the ''valleetee'' names translate to "''lee'' one", "''lee'' two", etc, similar to other cultures' "first month", "second month", and so forth.

[[folder:Web Comics]]
* ''Webcomic/CucumberQuest'' briefly demonstrates its [[http://cucumber.gigidigi.com/cq/page-313/ rather... distinctive]] dating system in the characters' journal entries. Days are regular numbers, but months and years are listed in wingding symbols.
* ''Webcomic/OurWorld'': The given year is 763, [[spoiler: even though the story is set hundreds of years in the future, after TheEndOfTheWorldAsWeKnowIt.]]
* ''Webcomic/ChildrenOfEldair'': Eldair has 405 days in a year, and Koe mentions being familiar with several calendar systems, but is wholly unfamiliar with the date Embera, who's from Earth, gives as her birthday, March 21, 2002. She then has to give him the general idea when it is in relation to the Spring Equinox in the northern hemisphere.

[[folder:Web Original]]
* In the ''Roleplay/LeagueOfIntergalacticCosmicChampions'', the year 3000 is the Year 0 of the New Calendar.
* ''WebOriginal/OrionsArm'' uses the Tranquility Calendar described below in Real Life. The setting extends to 10601 AT (~12570 CE).
* ''Literature/{{Tasakeru}}'': The in-universe calendar [[WordOfGod was intentionally designed]] to be roughly convertible to Earth-calendar format.
* The Literature/ChaosTimeline has the Sixtine Calendar (actually a subversion, since it's identical to the Gregorian), and ends up using 100 seconds per minute.
* {{Hadriex}} created one of these for ''VideoGame/TheLegendOfZeldaBreathOfTheWild'' in [[https://www.youtube.com/watch?v=TQ6jisr1Nlk&list=PLSQLREUw9vwlh8bzgvZCt_WS8615trN5H this parody]].

[[folder:Western Animation]]
* ''WesternAnimation/MyLittlePonyFriendshipIsMagic'' uses moons as a measurement of time, though it's never specified exactly how long this is. Common {{Fanon}} is that, much like other fantasy examples, one moon is equivalent to one month. Granny Smith mentions that it had been "over one hundred moons" since the last Apple family reunion, meaning about eight years had passed since the last one under this theory (assuming the same number of moons as in an Earth year).
* In an episode of ''WesternAnimation/{{Doug}}'', an extended fantasy sequence involving Quailman has a villain based on Mr. Bone, known as the Rulemeister, wipe out weekends from the timeline, forcing school students to attend school every single day (with no weekends on which to relax on). After Quailman defeats the Rulemeister by dropping a LogicBomb of sorts on the Rulemeister, Quailman brings back weekends and adds an eighth day, "Funday," to the week, something that the narrator erroneously describes as "slowing down the Earth's rotation."
* On ''WesternAnimation/JimmyTwoShoes'', all the months are [[{{Egopolis}} named after]] Lucius. (Lucember, Lucapril, etc.)
* ''WesternAnimation/TheSimpsons:'' One HalloweenEpisode had a flashback to a school board meeting on "the thirteenth hour of the thirteenth day of the thirteenth month. [[LampshadeHanging We were there to discuss the faulty calendars the school had purchased]]."
-->'''Homer:''' Lousy Smarch weather!
* On ''WesternAnimation/FamilyGuy'', NBC invented Catillsday so they could have another ''Dateline''.
* On ''WesternAnimation/{{Futurama}}'', the intro to the episode "Game of Tones" has a scene captioned Flomuary 24th, 3013, followed by Flomuary 39th and March 2nd.
* The land of Mewni from ''WesternAnimation/StarVsTheForcesOfEvil'' seems to have one; in "Mewnipendence Day", Star identifies the eponymous holiday as falling on "the 37th of Grobnock".
* Implied in the ''WesternAnimation/ThreeTwoOnePenguins'' episode "Practical Hoax" when Fidgel said that Bert Bertman was part of the class of 2222. Judging from the model of the car that Jason and Michelle rode in on their way to Grandmum's cottage, the show takes place at the dawn of the 21st century at earliest.

[[folder:Real Life]]
* Academic circles are prone to replacing BC/AD with BCE/CE ("Before Common Era"/"Common Era") to be more secular. Generally speaking a cultural non-starter with the general public, also liable to get certain Christian groups angry. The actual purpose behind the idea isn't really to avoid dating by Jesus,[[note]]No academic is dumb enough to pretend that's actually changing, what with the numbers being ''exactly the same''.[[/note]] but to not have to imply acceptance of a religion that you don't necessarily follow every single time you write the date: "AD" = "Anno Domini" = "year of Our Lord" (so writing AD is equivalent to saying "Jesus is my lord") and BC = "Before Christ" = "Before the Messiah" (so writing BC is equivalent to saying "Jesus is the Messiah"), and non-Christians occasionally get upset with the idea of needing to say what amounts to a small Christian prayer just to communicate simple concepts.[[note]]Interestingly, in the Arabic language, this problem doesn't exist: AD/CE dates are marked ''mīlādiy'', "of/after the Birth." This causes surprisingly few problems, since (1) "the Birth" doesn't directly say anything about Jesus, and (2) most Muslims don't have a problem with saying Jesus is the Biblical Messiah--he's just not God.[[/note]] Granted, this is more of a social statement regarding (and rejecting) the dominance of religion and religious iconography in general and/or this one in particular in [[LanguageEqualsThought language and thus culture]] than a scientific statement, but a statement nonetheless.
** Also popular with religious non-Christians using Western dating for comprehensibility reasons for similar but more doctrinal reasons.
** The reason why academics tend to prefer the "Common Era"-phrasing is because its start is entirely arbitrary, and is only followed due to a cultural custom, as Jesus was certainly not actually born in 1 AD or 1 BC,[[note]]Going by Literature/TheBible, it was somewhere between 7 BC and 4 AD.[[/note]] and even if he was, the concept of zero wasn't known in Europe when the dating was started, so they started counting from 1 AD, automatically putting all dates off by a year.
* The [[http://www.mithrandir.com/Tranquility/tranquility.html Tranquility calendar]], first postulated in Omni magazine, is a 13-month revision of the Gregorian calendar, with the 1969 moon landing as its zero point (specifically, the exact moment Neil Armstrong said "tranquility" in "Houston, Tranquility Base here") and 28-day months named for scientists, plus days outside the months and weekday cycle, Armstrong Day (20 July Gregorian) and Aldrin Day (29 February Gregorian, only in leap years). Dates are either "B.T." (Before Tranquility) or "A.T." (After Tranquility). For example, 2013-05-17 corresponds to 21 Kepler, 44 A.T..
* The French Enlightenment gave us August Comte's [[http://myweb.ecu.edu/mccartyr/pos-cal.html Positivist calendar]], which named every day and month after one of history's great men. The new regime created after the French Revolution adopted the same kind of calendar based on humanistic values and worked according to a simple mathematical system. Comte was born when this calendar was still in force.
* After her [[UsefulNotes/TheFrenchRevolution Revolution]], France tried a ''metric'' calendar, known as the [[https://en.wikipedia.org/wiki/French_Republican_Calendar Republican Calendar]] (''Calendrier républicain''). It consisted of twelve 30 day months, each divided in three ten day weeks, with five or six extra holidays at the end of the year. The years began on the autumn equinox (1792 being year I), and were reckoned on Roman numerals. While it was very logical, it wasn't too popular, for various reasons (mostly because ten-day weeks meant weekends were a lot rarer!), and only lasted twelve years--or less, considering that many people never really used it, and that even among those who did, the seven-day week was restored after a mere nine years after the Concordat of 1801 reestablished Sunday as a weekly festival. The names of the months and days of the week were changed, one of which (Thermidor, which lasted from July to August) is still remembered in the name of the dish Lobster Thermidor; otherwise, the French Republican months are mostly remembered from the French Revolutionary events, mostly coups (the most significant things remembered by the Republican Calendar are the Law of 14 Frimaire, centralizing power in the hands of [[ReignOfTerror the Committee of Public Safety]]; the Thermidorian Reaction, essentially a coup, bringing an end to the Terror; the Coup of Fructidor; the Coup of Floréal; and the Coup of Brumaire (in which Napoleon first seized formal political power). They also had a separate name for each [[http://en.wikipedia.org/wiki/French_republican_calendar#Days_of_the_year day of the year]], trying to mimic the calendar of saints with something secular -- in this case, plants, animals and tools. Which gave us day names like "pig" (Frimaire 5) or "manure" (Nivose 8) - yes, really, they had this. Now imagine all the teasing in school for kids born on these days.
** And not only that, but also the days themselves were decimally divided in ten hours, each new hour into 100 minutes, and each new minute into 100 seconds. This system was hardly ever used even by the government and quickly fell into obscurity.
** The French Republican Calendar was revived in 1870 by the Commune of Paris. It was abolished when the Communards were crushed about two weeks later.
** Some French history reenactors still use the Republican Calendar, and the calendars are still in print. Currently (AD 2016) we live in Year CCXXIV.
** The French frigates of the Floréal class all bear names of Republican months.
** The above French calendars were parodied to an extent by the [[http://user.icx.net/~richmond/rsr/pataphysique/pataphysique.html 'Pataphysical Calendar]], the calendar created by the Society of 'Pataphysics. It is a calendar of 13 months of 29 days (the last of which has no weekday and is imaginary most of the time anyway), which begins on the date of birth of the founder of 'Pataphysics, and which has among other things days named for Literature/DonQuixote and [[Literature/{{Foundation}} Hari Seldon]].
* The Soviets attempted something like this as well in the early 1930s, with five- and then six-day weeks. However, contrary to what some have claimed, they did retain the Gregorian months.
** Which was even more short-lived that the French system, mainly because at that point even the ''authorities'' doubted whether that was really necessary. They didn't even change the year numbering or month names or even the names of the days of the week (the "calendar reform" was really more about de-synchronizing the weekend: each worker would get one day in five or one day in six off, but it would be different for different workers). Bear in mind that in Russian, Sunday is ''Voskresen'ye'': "Resurrection."
* China used [[https://en.wikipedia.org/wiki/Ke_%28unit%29 decimal time]], similar to the French Republican clock, throughout its history before the 1912 revolution. The adoption of the Western calendar is widely considered a step ''backwards'' in China.
* UsefulNotes/FascistItaly too had its very own calendar, in which 1922 marked the year zero; therefore, 1936 became XIV E.F. (that is, the fourteenth year of the "Fascist Era"). Remnants of this calendar can still be seen on the façades of many public buildings throughout Italy.
* There have also been attempts to create calendars for other planets (and moons) in the solar system in case we need to live there someday. The most developed is the Darian calendar for Mars, which has 24 months of 28 Martian days each (called ''sols'', so we [[TwoOfYourEarthMinutes don't confuse them with Earth days]][[note]]JPL and NASA use sols in tracking Mars missions: the activities of rovers are reported as, say, occurring on sol 43 since that rover landed.[[/note]]). There's ''already'' been arguments on what epoch to use (i.e. when Year Zero was); the Darian currently uses the Telescopic Epoch which is the Martian year corresponding to March 1609 - January 1611 CE, but originally used an epoch based on the landing of Viking 1 in 1976.
* Calendars (by the same guy that did the Darian calendar for Mars) have also been proposed for the Jovian moons:
** Io: 24-month year, with 32 "circads" (fractions of the solar day that each roughly correspond to the length of the human wake/sleep cycle) per month, an 8-circad week, 40 circads in the twelfth month (and the 24th month in leap years).
** Europa: 24-month year, 8-circad week, with 32 circads per month, plus a week in month 24 in leap years.
** Ganymede: 24-month year, 8-circad week, with 32 circads per month, minus one week in month 24 in non-leap years.
** Callisto: See Io.
* The Japanese Era system, since 1872, has been based off of the lives of their emperors, beginning at the moment of the emperor's accession and ending with the incumbent's death. This makes eras fairly short, and if you're not versed in Japanese time systems, causes misunderstandings.
** Before the Meiji Restoration, eras could be changed at will, some lasting only a year or less. They were usually changed after a major event (sometimes to hopefully throw off the taint of whatever had occurred in the previous era).
** The last time when an emperor died (Hirohito, 1989), the Japanese computer programmers had to change the value for "era" from "Showa" to "Heisei" everywhere. Just like the [[MillenniumBug [=Y2K=]]] bug.
** To search the Japanese patent database for patent applications published before 2000, you need a letter prefix for the era (S or H), a two-digit number for the regnal year, and a publication number that restarts at 1 every year. For patent applications published in 2000 and later, you use the Gregorian year and the publication number that restarts at 1 every year.
** Japan has another (generally obsolete) system that numbers the years based on the ascension of the legendary Emperor Jimmu in 660 BCE. This is why Japan was so keen on getting the 1940 Olympics in Tokyo; it would have been the year 2600 by their reckoning.
* Religions sometimes use different calendars to calculate holidays:
** Many Orthodox Christian churches still follow the Julian calendar, which is thirteen days different from the Gregorian, with the difference growing at a rate of 3 days every 4 centuries. Some have switched to the Gregorian calendar, while others have adopted the so-called "Revised Julian" calendar, which has century years non-leap years except those leaving a remainder of 200 or 600 when divided by 900, which are leap years (the Gregorian has century years non-leap years except those divisible by 400, which are leap years). This system is synchronised with the Gregorian until 2800.
** Judaism follows a ''lunisolar'' calendar (one that is both solar and lunar), built around the New Moon as the start of the month, and counts years from the Biblical date of the creation of the universe[[labelnote:*]]Before anyone gets the wrong idea, the vast majority of modern Jews--even the Orthodox--do accept that the Earth is not 6,000 years old, but also see no need to change their epoch date. Besides, even if they wanted to, [[JewsLoveToArgue you couldn't get everyone to agree on a new epoch date]], so might as well not broach the subject.[[/labelnote]] (2008 corresponds to 5768/9 -- the New Year is in September or thereabouts - aiming for Autumnal Equinox). The calendar uses a 19-year Metonic cycle, adding leap months in a set sequence of years, in order to keep all holidays falling in the same seasons. The calendar was originally invented by Greek astronomer Meton in the 3rd century BCE.
*** The Buddhists use a similar calendar. Incidentally, they both use the same dates.
** The Muslim (or Hijri) calendar has 12 lunar months in a year of about 354 days. Because this lunar year is about 11 days shorter than the solar year, Islamic holy days, although celebrated on fixed dates in their own calendar, usually shift 11 days earlier each successive solar year, such as a year of the Gregorian calendar. Islamic years are also called Hijra years because the first year was the year during which the Hijra occurred - Islamic prophet Muhammad's emigration from Mecca to Medina. Thus each numbered year is designated either H or AH, the latter being the initials of the Latin anno Hegirae (in the year of the Hijra). For example, AH 1433 is approximately 26 November 2011 (CE) to 15 November 2012.
*** The Islamic year 20874 AH will be the same year as 20874 AD.
** A rather peculiar one is the Iranian calendar. It can justifiably claim to be both one of the oldest and one of the newest calendars in wide use. Oldest, because the Iranians have had some sort of unique calendar for as long as they've been around, and the Persians have been around since at least 700 BCE; at least one of the old Persian calendars remains the official calendar for Zoroastrian worship, and more to the point, the current calendar draws on innumerable ancient sources for its accuracy. Newest, because its basic principles were laid out in 1079 (CE), and the current form of the calendar was adopted in 1925 (CE). It combines the mathematical/calculating elements of the Hindu calendar (the most important of which is a highly complex system of calculating when to have the next leap year) with the ancient Iranian calendar providing the date of the new year (the ancient spring festival of Nowruz, on the vernal equinox, during which men jump over bonfires and hope their crotches don't get set alight), and the Islamic epoch date (i.e. Year Zero is the year of the Hijra). As a result, the Iranian calendar is often called the Solar Hijri calendar. The Solar Hijri year for 2011-2012 is 1390 (note the 42-year difference between it and the Islamic, or Lunar Hijri year!).
** Discordians have a calendar that is divided into five 73-day seasons (Chaos, Discord, Confusion, Bureaucracy, Aftermath), with five-day weeks (Sweetmorn, Boomtime, Pungenday, Prickle-Prickle, Setting Orange), and two holidays a season, one on the fifth day and one on the fiftieth. The zero-point of the Discordian calendar is 1166 BCE, so 2008 AD would be 3174 Year of our Lady of Discord. Every fourth year includes a leapday analogue called St. Tib's Day, which has caused some unintended mathematical confusion as to whether the Discordian Calendar is meant to align with the Gregorian or Julian calendar (This being the Discordians, the answer is probably "yes").
* ThoseWackyNazis tried to replace the Latin-derived months' names by more "Aryan" ones. This was the brain-child of [[https://en.wikipedia.org/wiki/Georg_Ritter_von_Sch%C3%B6nerer Georg von Schönerer]] (a late 19th-century antisemitic and far-right radical from Austria), and is from long before the Nazis' time.
* In the Finnish language, every month really is called "______ Moon" (''-kuu'' in Finnish). For example, August is ''Elokuu'', "Harvest moon" and December is ''Joulukuu'', "Christmas moon".
** The same is true in Chinese. first-moon, second-moon, third-moon, etc. (一月,二月,三月...) Days of the week are handled similarly: 星期/周一,周二,周三.
*** As well as in Japanese, although some of the day names, despite being written in a regular way with the characters for the number and "day", are pronounced irregularly: the first day of the month is tsuitachi, and pronunciations are based off native Japanese numbers instead of the ordinary (Chinese-derived) readings for the 2nd through 10th, as well as the 14th, 20th and 24th.
*** Japanese also has traditional month names, like 神無月 'Kannazuki' (godless moon), 文月 'Fumizuki' (letter moon), and so on. Three of them don't end in -zuki (moon), 弥生 'Yayoi', 師走 'Shiwasu', and 如月 'Kisaragi' (although the last is written with 'moon').
* Some Christian congregations have been known use terms like "First Day", "Second Day", and so on, rather than names like "Thursday" and "Saturday" that have pagan origins (honoring the Norse god Thor and the Roman god Saturn, respectively). They have been known to give the same treatment to the names of the months, to avoid naming Roman gods or emperors.
* And not just congregations, but whole Christian cultural spheres, such as Portuguese and Estonian. They have numbered week days, and Saturday is either "sabado" (Sabbath) or "lauapäev" (cleansing day) and Sunday is "domingo" and "pühapaev" (Lord's Day) respectively.
** In Modern Hebrew the days never had names but always had numbers. They're just called "Day First", "Day Second", "Day Third" and so on until the seventh day, which has the name "Shabbat" or "Sabbath". And this is the case not only in modern, but also in medieval, Mishnaic and Biblical Hebrew, inasmuch as we see days of the week named.
*** The custom is common among Semitic languages; the Arabic days of the week (Al-Ahad, al-Ithnayn, al-Thulatha'...) mostly translate to "First, Second, Third...," but Friday is "al-Jumu`ah," or "Gathering" (because it's the day of praying together in the mosque) and Saturday is "al-Sabt". ''Al-Sabt'' comes from the same common the same root as "Shabbat," which appears to be influenced by (but not directly derived from) the common Semitic root S-B-` (realized in Arabic as ''saba`ah'' and in Hebrew as ''shev`a''), as both Hebrew and Arabic reckon Sunday as the "first day" of the week and the Muslim Sabbath was on Saturday (and Muslims prayed toward Jerusalem) until the Jews of Medina pissed Muhammad and the Muslim community off. At that point, they changed the direction of prayer to Mecca (an almost literal about-face--Medina is about halfway between the two) and changed the Sabbath to Friday (honoring the last day of creation, on which He created Man), which became ''al-Jumu`ah'' to reflect this change (to pagan Arabs, Friday was ''al-Suds'', "Sixth Day", while Saturday was always ''al-Sabt'', reflecting common Semitic tradition). Interestingly, this allows the days of the week to line up with the workweek in some countries; some Arabic-speaking countries (e.g. Egypt) have Friday-Saturday weekends, meaning that the workweek starts on "First Day."
*** Sunday, Monday, Third Day sounds silly - to English speakers. Nevertheless, that's what happens in Slavic languages, such as Polish, which goes Niedziela (Rest), Poniedzialek (After Rest), Wtorek (Tuesday - second), Sroda (Wednesday - Middle), Czwartek (Thursday - fourth), Piatek (Friday - fifth) and Sobota (Sabbath). Russian works similarly, with the substitution of Voskreseniye - Resurrection - for Sunday. The two modern Baltic languages, Latvian and Lithuanian, ''have'' however ditched the non-numeral names and just number the week Firstday to Seventhday from Monday to Sunday respectively.
* Also strange respecting Arabic calendars: the names of the Gregorian months in Arabic. Virtually all Arabic-speaking countries officially use the Gregorian calendar for business and agricultural purposes (the Islamic calendar being relegated to religious use only in every country except Saudi Arabia), and different countries have their own set of names for the months. Egypt, Sudan, and the countries of the Arabian Peninsula that aren't Saudi Arabia have names adapted directly from the Latin: ''Yanāyyir'' for January and ''Aghusṭus'' for August make this fairly clear. On the other hand Levantine (Syrian/Lebanese/Jordanian/Palestinian) and Iraqi Arabic use names taken from the ancient Semitic lunisolar calendar, which are very similar to the names of the Hebrew months for a similar period: for instance, February is called ''Shubāṭ'' (compare Hebrew ''Shevat'' for a winter month typically falling in January-February) and July is called ''Tammūz'' (compare Hebrew, er, ''Tammuz'', typically falling in June-July). Tunisia and Algeria, in the meantime, have a strong French influence and that's reflected in their month names: compare Algerian/Tunisian ''Jānfī'' to French ''Janvier'' ("January") or Algerian/Tunisian ''[='=]Ūt'' to French ''Août'' ("August"). Finally, the Berbers and peasants of Morocco had actually retained the Julian calendar for centuries under Muslim rule for agricultural purposes, and had their own names derived from the Latin for the Julian/Gregorian months unique to the country. See, e.g. ''Ghusht'' for August and ''Dujanbir'' for "December." The strangest one is Libya, which historically used the standard that existed in Egypt, but when UsefulNotes/MuammarGaddafi took over, he invented a new set of names out of whole cloth. These names were abolished in 2011 after the revolution, but so far nobody's gotten around to officially picking which system of month names the country would use.
* Armenians (traditionally) use a calendar based on the {{Ancient Egypt}}ian one, with twelve 30-day months (and five monthless days) each day of the month having its own name, starting in 552 AD.
* Interestingly, the Egyptian one is still used by the Coptic Orthodox Church as the [[http://en.wikipedia.org/wiki/Coptic_calendar Coptic calendar]]. AugustusCaesar modified it to be in sync with the Julian calendar, but that's about all that's changed since the days of the Pharaohs.
** Most modern Egyptians--both members of the Coptic Christian minority and Muslim majority--are barely aware of this calendar's existence, using the Gregorian calendar for almost everything. The Coptic calendar and Islamic lunar calendar are mostly only considered when it comes to the timing of religious festivals (plus [[http://en.wikipedia.org/wiki/Sham_el-Nessim one secular festival linked to a religious one]]). However, the Gregorian calendar is a fairly recent introduction, being instituted sometime in the 19th century (probably by the Khedive Ismail, who tried to be more European than the Europeans themselves). Before that time, Egyptians Muslim and Christian alike used the Coptic calendar for agricultural purposes: the months are coordinated with the significant events of Egypt's unique agricultural situation, including the floods of the Nile and the rains (which are so regular that you can predict almost to the day what the weather in Alexandria will be like a whole ''year'' in advance).
** Another interesting tidbit: the Coptic Church uses as its epoch the accession of the [[UsefulNotes/TheRomanEmpire Roman Emperor]] Diocletian (in 284), noted for his persecutions of Christians, which by that time was very strong in Egypt. As a result, the Coptic calendar is often marked with the abbreviation A.M.--''Anno Martyrum'' (Year of the Martyrs).
* There are ''dozens'' of calendar systems in place, including the Chinese Calendar, Jewish Calendar, Hindu calendar, the Zoroastrian calendar, the Ethiopic calendar, and several other local ones. Just look it up on Wiki/{{Wikipedia}}.
** Basically, if there is an ethnic/cultural holiday called XX "new year" and that falls on different days of the year every year, that means that that ethnic/cultural group has a different calendar system.
* A mild example: South Asian magazines, trade periodicals, academic journals, etc. that are published on a quarterly/seasonal schedule (of which there are [[ArchivePanic a surprising number]]) often identify each issue as "Autumn," "Winter," "Spring"...or [[WhenItRainsItPours "Monsoon"]].
* Although computers generally use the Gregorian calendar to display dates to the user, internally, most software represents time as an integer number: the number of seconds or milliseconds since 1 January 1970, the so-called UsefulNotes/{{UNIX}} epoch. This has in turn led to speculation about a possible [=Y2K=]-like phenomenon where the UNIX time [[http://en.wikipedia.org/wiki/Year_2038_problem variable overflows]], which could happen around year 2038 if a signed 32-bit integer is used to represent seconds. Modern systems are just now becoming 64-bit, which'll last for about another 300 billion years. Whether all software gets converted over to 64bit before 2038 is another issue, however.
** However, since the UNIX timestamp second count is kept in sync with UTC, which uses occasional leap seconds to keep it consistent within a second of Greenwich Mean Time, the numeric value of this count is not exactly equal to the actual number of elapsed seconds, because the count is defined so that there are always 86,400 seconds in a day, so any leap seconds are skipped in the count.
* In Basic programming, dates are stored as a double-length decimal number representing the number of days from 1/1/1900. This is why in Excel or Access, to add a day, you simply do "Date+1". This does not easily take into account daylight savings time, as non-existent times can be shown during the skip forward, and there is no distinction between the first and second version of 2-3AM during the skip back.
* Most natives of the Arctic Circle have traditionally described time's passage in terms of "sleeps", as days' actual duration varies too widely at high latitudes to be a reliable measurement.
* Infamously, Pol Pot's 'Democratic Kampuchea' created a "Year Zero" (1975, when he seized power) during his genocidal rule of Cambodia.
* Historians writing about Rome (both at the time and more recently) sometimes use AUC, ''AbUrbeCondita''="from the founding of the city (of Rome)", dating years from the traditional founding of Rome in 753 BC. This system has been copied by various writers with different cities. However, Romans usually reckoned years by who was emperor. In the Republican era and early empire, years were named for the two consuls, which may be just as well, as nobody knows exactly when Rome was founded. (The bit about Republican years being named after the two consuls led to a joke that the year UsefulNotes/JuliusCaesar was Consul--59 BCE--was the "Year of Julius and Caesar," since he completely overshadowed his co-consul Bibulus).
** Which makes the Gregorian Calendar a meta-example of this. The average Roman tended to recon their time with the Emperors, and since Christ is the King of Kings...
** The Roman calendar originally also had an interesting peculiarity: the version established by Romulus only had ten months, Martius (March) through December. The days between December 30 and Martius 1 were just "winter days" which weren't assigned to any month. (When Numa Pompilius reformed the calendar ~40 years later, these days did get assigned to months, Ianuarius and Februarius; although he put the months at the end of the year, eventually people started treating them like they were the beginning of the year for certain purposes, e.g. installation of consuls, which is why ''Oct''ober is the ''10''th month of the year.)
* [[http://en.wikipedia.org/wiki/Renaming_of_Turkmen_months_and_days_of_week,_2002 Turkmenistan's rubber-stamp government decided to rename their entire calendar, INCLUDING the days of the week, in 2002.]] This was a basic decree by their somewhat insane leader, Saparmurat Niyazov, aka the Turkmenbashi and [[CloudCuckooLander one-time administrative assistant to the Mayor of Cloudcuckooland]]. Since his death, such decrees have been removed from the legal code.
* The North Korean calendar begins with the birth of [[PapaWolf Kim Il Sung]] (1912 AD) as year Juche 1 in Gregorian format; all pre-calendar history uses the Gregorian calendar.
* By a stunning coincidence, the Chinese system of reckoning the year by the years of the reign of the Emperor has led to the Taiwanese calendar being precisely in sync with the Juche one: the Republic of China (aka Taiwan) elected to continue the era-name system, using "Minguo" (Republic) as the name. Since the republic was founded in 1912, each Minguo year has the same number as the corresponding Juche year (2010, for instance, being both Minguo 99--the 99th Year of the Republic--and Juche 99). This has led to the somewhat amusing [[http://en.wikipedia.org/wiki/Y1C_Problem Y1C Problem]] for Taiwanese computer systems (which use the Minguo year).
* In AncientGreece, every polis had its own calendar, with years named after government officials (like ephors in Sparta or archons in Athens). These calendars were very often very quirky (for instance, Athens had a calendar of ''ten'' months, which had some interesting connections to the Athenian constitution).[[note]]If you must insist, the citizens of Athens were divided into ten tribes. Every year, 50 male members of each tribe were selected--by lot!--to sit on the "Council of 500", aka the ''Boule''. The ''Boule'' set the agenda of the ''Ekklesia'', or Popular Assembly (the assembly of all free male citizens of Athens, which had final authority on everything), and certain other responsibilities as well. Of these, the most important was that of sitting vigil. Each of the ten Athenian tribes was assigned a month. During that month, its 50 members of the ''Boule'' were expected to remain at the ''Boule''[='s=] building day and night in order to respond quickly to any crisis that might arise. Convenient, isn't it, that there were ten months and ten tribes?[[/note]] Oh, and that was just ''one'' of Athens' calendars; the ten-month solar Athenian political calendar, used for scheduling state business, ran in parallel to the twelve-month lunisolar Athenian festival calendar, used for religious and agricultural purposes. And we repeat, ''each'' state had at least one calendar of its own, and some also had more; keeping track must have been a headache with over a thousand different states in place. The historians sometimes used the Olympic games for counting the years, but no one else did.
* Javanese people in Indonesia use month names taken from the Islamic calendar. The month names are Sura (Muharram), Sapar (Safar), Mulud (Rabi al-awwal), Bakda Mulud (Rabi al-thani), Jumadil Awal (Jumada al-awwal), Jumadil Akhir (Jumada al-thani), Rejeb (Rajab), Ruwah (Sha'aban), Pasa (Ramadhan), Sawal (Shawwal), Sela (Dhul al-Qi'dah) and Besar (Dhul al-Hijjah).
* In Starhawk's novel ''The Fifth Sacred Thing'', the largely neo-Pagan community in a future UsefulNotes/SanFrancisco refers to August as "Third Foggy Moon". (This is drawn from a San Francisco calendar Starhawk proposed in her nonfiction book ''Truth or Dare'': as a substitute for the "traditional" neo-Pagan months, she worked a set of month-names appropriate to the place and time where she was working. The three full moons of summer are "Fog Rolls In Moon", "Fog Sticks Around Moon", and "Fog Sticks Around Some More Moon".)
* The whole concept of "days" as standard units of calendar time breaks down in the hearts of the Arctic or Antarctic Circles, where the sun either doesn't rise or doesn't set for a sizable fraction of the year. Expeditions to the Poles that don't make a steady effort to adhere to reliable clocks usually wind up operating on their own sleep/wake cycles, which quickly fall out of step with a 24-hour day (mainly because, without a correcting reference, the natural human circadian rhythm drifts from the rotational day a little bit each day).
* Numerous attempts have been made to [[https://en.wikipedia.org/wiki/Calendar_reform replace the Gregorian calendar with something neater]], with the movement being strongest in the 1920s and 1930s.