Hit So Hard the Calendar Felt It
It's The End of the World as We Know It
, and The End of the Beginning
as well. Either the few remnants of sentient life (we're talking either Class 1 or 2
here) are rebuilding, or some Reality Altering Event
has taken place which reshapes their entire conception of History. In any case, they see fit to reset the calendar
and set civilization's New Beginning as Year Zero
(or year one).
Can also be revealed to have happened in retrospect as a World Building
trope - the event after which a society dates its calendar tells you something about their culture.
Not to be confused with people being "punched into next week".
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- The Gundam franchise loves using alternate calendar systems, but the only one that really matches this trope is Gundam X, which is set in After War 0015, 15 years after the disastrous end of the 7th Space War which wiped out 90% of humanity. Some fan theories suggest that Gundam Wing's After Colony calendar started with the launch of Skylab, but there isn't any official proof that this is true or not. Special mention to Turn A Gundam, which implicitly has several dozen calendar changes in its backstory, to the point where this trope is the only explanation.
- Some Gundam universes have more concrete explanations. The Future Century or FC of G Gundam is based on the establishment of the world government that currently oversees international affairs as well as calls for the Gundam Fight every four years to determine which Neo Nation has ruling power for the interim. This after apparently lots of brutal fighting finally brought those countries to the peace table to hammer out some way to institutionalize their constant conflicts. The series takes place throughout the year FC60, which is marked as the year of the 15th Gundam Fight.
- Also, one Gundam series averts the trope. Mobile Suit Gundam 00 sticks with Anno Domini.
- Also seems to be the explanation for Gundam Reconguista In G's Reguild Century, in which the backstory vaguely mentions cataclysmic wars, environmental disasters and famines so severe people had to resort to institutionalized cannibalism in the final moments of the Universal Century calendar.
- The setting of Battle Angel Alita: Last Order marks time according to the Era Sputnik, counting from the launch of the Sputnik 1 in 1957. The story also informally refers to years in the "Anno Koyomi" — because the background character, Koyomi, was born the same year that the series began with Alita's rebirth.
- Nobody remembers what year it is in The Big O because everyone was hit with Laser-Guided Amnesia forty years ago. As a result, people tend to refer to the date by referencing the loss of memory, "X years ago".
- One of the proofs that the Holy Britannian Empire is the most dominant force on Earth in Code Geass universe, the calendar doesn't follow the real world AD/CE - instead, we have A.T.B, for "Ascension to Throne, Britannia". This roughly coincides with about -60 BC, when the in-universe history diverges (the reason being that Julius Caesar never conquered Britain; the Anglo-Saxons elected a "super leader" to fight him instead and won, amongst all the historical variance in that universe which included a failed American Revolution and a change of seat of power from mainland Britain to American Colonies).
- In Lyrical Nanoha, the new Mid-Childan calendar begins after the Ancient Belka War, which ended when the dominant Ancient Belka Empire destroyed itself and rendered their planet uninhabitable due to a combination of infighting and the Lensman Arms Race, leading to the banning of mass-based weapons on all dimensions.
- At some time, possibly after the War with Them, the Sora No Woto calendar was changed to A.P.
- The calendar was reset at some point in From the New World, due to the long dark ages of mass slaughtering by psychics. They're currently in the 200's. It actually seems to have been running for roughly the length of Tomiko's life, and may have been reset again because of K's rampage. There doesn't seem to be much communication between distant villages, either, so they may all be using different calendars.
- Some unknown event caused the calendar to reset in Attack on Titan over 850 years ago. Oddly this doesn't match up to when the titular titans appeared or when they they built the walls that protect the last vestige of humanity.
- Transmetropolitan takes place at some unspecified year in the future. No one ever refers to a specific year; it's always in reference to other events. At one point, we're told that a Revival truly lost it when she asked what year it was, and "they told her." It's not stated outright, but what they probably said was "we have no idea."
- The "Ultimatized" Marvel 2099 seen in Timestorm 2009-2099 includes a brief scene set some years earlier with a holographic teacher modeled on Reed Richards explaining that it probably isn't really 2085 because they started counting again from the last date before the disaster.
- The Hypernaturals by Dan Abnett and Andy Lanning is set in the year 100 AQ (Anno Quantinuum), a century after The Singularity.
Gondorians: *change calendar*
- In With Strings Attached, the planet C'hou underwent some kind of big shakeup about five hundred years previously. Among other things, it seems to have removed all concept of calendars and clocks from Baravada.
Films — Animated
- Titan A.E.: The movie begins A.D. 3028 and ends 15 years later, in the year 15 A.E. (After Earth).
Films — Live-Action
- In 2012 the surviving Humans reset the calendar after the Cataclysm.
- Similarly, in Cloud Atlas (both the book and the movie) some of the events take place 106 years After The Fall. What exactly was the Fall is never explained though.
- In the '50s movie When Worlds Collide, a rogue planet passes by Earth and destroys it due to tidal effects, but the passing planet itself is inhabitable. In the end, a few people land on it to
repopulate it, and an ominous Bible-like title card says this is Year One.
- In Star Wars, time is divided into BBY and ABY, before and after the Battle of Yavin (in order to distinguish prequels from the original trilogy).
- The Expanded Universe gives at least two more times this happens prior to Yavin (namely, the respective foundings of the Republic and the Empire). Luke complains about it in The Thrawn Trilogy, as it makes reviewing historical records rather tedious.
- In Land of the Blind, the calendar is reset with the year of the revolution as Year Zero. The film begins in Year Minus Five.
- The film Panic in Year Zero! gets its title from the decision of the United Nations to reset the calendar after World War III went off-the Title Drop is a declaration heard by the main characters on an update broadcasted through the CONELRAD emergency broadcast system.
- Multiple science fiction stories in the 1950s and 60s postulated that at some unspecified point in the future, mankind would reset the calendar to start with the detonation of the first nuclear warhead as year one. This went out of fashion rather quickly as soon as the dangers of fallout became widely known.
- The Orphan Master's Son is set in North Korea, where the calendar is dated from the birth of Kim Il Sung in 1912 (see Real Life below).
- Edgar Pangborn's Davy and related stories take place in North America centuries after a 'limited' nuclear and biological war. Some years after the war a prophet named Abraham arose, and the church founded on his martyrdom established a new calendar from that date, with The Year of Abraham replacing Anno Domini.
- The Dune books did something analogous, resetting the calendar when the Spacing Guild established its monopoly (which was about 108 years after what might have been regarded as the apocalypse — the end of the Butlerian Jihad).
- In Drowtales, the current story takes place in the year 1098 of the Moonless Age. Not because the moon was destroyed 1100 years ago, but because the elves went into exile underground where they couldn't see the moon.
- In Lord of the Rings, the story begins in the year T.A. 3018, where T.A. stands for "third age" (meaning they'd already reset the calendar at least twice), and by the end of the story, a fourth age is declared.
- The Legend of Rah and the Muggles has the calendar being reset by a nuclear war. The problem is that they talk about the "year of the purple haze" [nuclear fallout]. Every single year in living memory has been the year of the purple haze!
- In The Stand, Randall Flagg tells the date as "this thirtieth day of September, the year nineteen hundred and ninety, now known as The Year One, year of the plague."
- The Turner Diaries is set in 1991 and 1993. During the epilogue, it is explained that around the year 2000, they reset the year to coincide with the annihilation of all minorities.
- In The Bible, the events of Passover shifts the calendar to starting the year at that month.
- In The Wheel of Time, the historical records show several calendars being used. This has happened 3 times in recorded history: The end of the 2nd Age and the Breaking of the World, the Trolloc Wars, and the Hundred Years War. The story occurs at the end of the 3rd Age, so the calendar is likely to reset again.
- In Charles Stross' novel Scratch Monkey, by the time of the book's setting (several thousand years from now), there have been so many rulers declaring new eras and new calendars that "Year Zero Man" has become the standard term for a totalitarian dictator.
- In Tamora Pierce's Tortall Universe, the numbers of the years are followed by "H.E.", short for "Human Era"- the time after the Immortals were banished to the Realms of the Gods.
- In the Codex Alera series, it is eventually revealed that the calendar is reset by the events of the series.
- The hyperconsumerist society in Brave New World worships Henry Ford, and dates its calendar from the release date of the Model T.
- In The Belgariad and its sequel, The Mallorean, the calendar used dates the year 0 to be when the evil god Torak cracked the world. This particular calendar is referred to as the Alorn calendar, implying that other nations may have different systems.
- The Tolnedrans at least are implied to date by dynasty.
- The Dals measured time in "Ages", which only ended when something momentous to their grand mission occurred. The cracking of the world corresponded to the end of their First Age, and the books take place in their Fifth Age.
- The Mortal Engines quartet by Philip Reeve have all dates measured from TE - Traction Era, ie. the time from which cities started moving around gobbling each other up.
- In Honor Harrington, the Galaxy at large uses the Ante/Post-Diaspora calendar, which shifts the epoch to 2103 CE at the launch of the first colony ship, the Prometheus, but is otherwise a standard Gregorian calendar, measuring in T-years (Terra years) and T-centuries and so on.
- Many planets also have their local calendars, usually dating from their founding (Manticore, for example, has the AL system, based on the arrival of the Jason in the Manticore Binary System and keyed to Manticore's orbit of 1.7333 Earth years to the year, in some official documents), but everybody respects the Diaspora calendar...except backward places like Grayson, which still uses the pure Gregorian calendar (which is particularly annoying because "AD" means "Ante Diaspora" to everybody else, so "4000 AD," which is around where the series takes place, means roughly 2000 BCE to non-Graysons...). Consider that the Graysons are the only ones shown to still use the American system of measurement (necessary for playing baseball correctly), as well as the only ones barbaric enough to still consider neckties fashionable.
- Manticore is actually indicated to have three different calendars, one for each of the inhabited planets in the home system, Manticore, Sphinx, and Gryphon (which have significant differences in the length of their years). That said, everyone on the latter two planets keeps a reckoning in both AL and their local calendars, as well as the Post-Diaspora calendar. Which is easy enough in a highly computerized society, just have your chrono show all three relevant times.
- Riddley Walker uses the O.C. system, which stands for "Our Count."
- Implied as Tally and Zane look at Rusty graffiti in the second book of the Uglies trilogy.
- The far-future bits of the Enderverse (Speaker for the Dead, Xenocide, Children of the Mind, and some short stories) dates events from the foundation of Starways Congress, the interstellar pan-human government established 1180 years after Andrew "Ender" Wiggin defeated the Buggers (an event implied to occur sometime between the 24th and 27th centuries AD). Speaker for the Dead starts in the late 20th century SC.
- H. Beam Piper's Terro-Human Future History used Atomic Era dating, with 1942 AD note as Year 0.
- Larry Niven's Svetz the Time Traveler use Atomic Era dating as well, with the same starting point.
- Ian Stewart's Hoard of Mathematical Treasures includes a "Future History of Mathematics", which parodies the genuine "History of Mathematics" earlier. Towards the end (after 11828 AD) we get "0: Reformation of the calendar", but what caused this is unknown. (Although it does seem to occur shortly after human civilisation rebuilds itself from machine rule.)
- In Murderess, the people of the parallel world Greywall’d count years since Signus’ Fall. Lu, the protagonist, came from Earth, and is a bit surprised to hear it’s not the year 2012...
Live Action TV
- Blake's 7 takes place in the third century of the second calendar. It's never quite clear why they stopped using the first calendar, though.
- Star Trek reckons dates in Stardates, as Stardates are supposed to a unified system in a Federation where planets have different days and years, and where starships travel at relativistic speeds and can be affected by time dilation.
- There is a bit of Canon Discontinuity because of the differences in uses between the events of the original series and the time of The Next Generation By the time of the latter, the Stardate timeline became more firmly established, with Stardate 41000 being the beginning of Earth year 2364 and advancing steadily so that 1000 passed by the beginning of the next Earth year. All events within the continuity of The Next Generation (including Deep Space Nine, Voyager, and the three TNG movies) obey this timeline.
- The writer's bible for TNG says that the "4" in "41000" signifies the 24th century, and the TOS stardates really started with 3, but it was just omitted in practice. However, this lost sense when the events of the TNG universe crossed into their 11th year; however, people by then were used to the above system, so Stardate 50000 passed without much discussion.
- The 2009 film throws even more Canon Discontinuity into the mix by changing the Stardate system yet again. The reboot abandons the system established in TNG for a system where the Stardate always matches the year on Earth. Even events that took place on the original timeline use the new system. As a result the future events involving Spock and Nero take place on Stardate 2387.XX (the system established by the Abrams film) instead of 64XXX.XX (the system established by TNG and it's spinoffs). This may be an attempt at resolving the original discontinuity by using the new reality to allow for some Hand-Waving.
- Fridge Logic can set in when you realize that Spock, knowing the system in use from his own time in the 23rd century, automatically extrapolated that system out to the future and did the mental conversion for Kirk's convenience.
- First Edition Paranoia: Dates were sometimes in the form of "Year 240 of the Computer"; i.e. 240 years since the Big Whoops (destruction of world civilization) and the takeover of Alpha Complex by the Computer.
- It became even weirder in later editions where it was implied that, due to some sort of glitch, EVERY year is "Year 240 of the Computer". Although anyone who pointed this out would be implying that the Computer is defective, which is, of course, treason.
- In a fairly realistic fashion, the Greyhawk campaign setting actually has several calendars, most of which are associated with ancient and now-defunct civilizations. The "Common Year" calendar currently used by most of the Flanaess is based on the crowing of the first Overking of the Great Kingdom of Aerdy, which was the first major nation to emerge in the aftermath of what was basically a magical nuclear war that forced lots of people to migrate to new lands.
- Years in Dragonlance are numbered from the Cataclysm.
- One of Forgotten Realms' several calendars is "Present Reckoning", started on Time of Troubles.
- It never caught on, though. This fact is mentioned only once in the 3rd Edition books and everything else from then on is only the standard Dales Reckoning.
- Exalted had its timeline initially measured in years pertaining to the Age of Man, when the Primordials were overthrown and the Solar Deliberative was established. When the Solar Deliberative fell during the Usurpation, the Shogunate fiddled with an alternate calendar. At least until the Great Contagion fucked with that and the Scarlet Empress ended up unifying various daimyos into the Realm, which is why the calendar currently uses RY (Realm Year) to designate how many years it's been since she took the throne.
- The calendar system basically says, "It has been X years since the last world-shaking cataclysm."
- It says something when the calendar used by Autochthonia (which started somewhere in the days of the Solar Deliberative and hasn't been reset since) has a current date that's several thousand years farther along than the one currently used in Creation.
- The German RPG Das schwarze Auge (Realms of Arkania) had the main realm count the years by the current Emperor. By now reckoning has been changed (back) to the 'BF - Fall of Bosparan' reckoning, counting from the fall of the former empire. There are also numerous other calendars around in that world, counting from the first landing of gildenland settlers, the independence of countries, the threat of a catastrophe by a messenger of the gods to a city, and so on.
- Eclipse Phase uses AF (After Fall), mostly as a way to avert Exty Years from Now. ("The Fall" being when a bunch of crazy AIs nearly wiped humanity out.)
- On Dominaria, the default world of Magic: The Gathering, most nations use the Argivian Reckoning calendar, which sets Year 0 at the year the Brothers, Urza and Mishra, were born (Urza on the first day of the year, Mishra on the last). They were the leaders of the opposing forces in the Brothers' War, which destroyed multiple kingdoms, wrecked the continent of Argoth, and ushered in the Ice Age.
- Rifts's Post-Apocalypse calendar came about when enough people realized that they had enough time and energy left over from trying to survive after The End of the World as We Know It (two or three centuries after it actually happened) to care about trivial matters like what year it was. The P.A. calendar is distinctive to North America, specifically the Coalition States and the surrounding area however. Some nations that weathered the Great Cataclysm better, most notably the New German Republic, are still using the Gregorian Calendar.
- Ironically, averted in Warhammer 40,000, which still uses our current calendar without even a token epoch shift. Though heavily modified (it's the only well-known calendar that takes into account the uncertainty of timekeeping in the multistellar empire), it's still the good old Gregorian calendar based on the Earth year and the birth of Christ. Probably they still use it because it's one of the few things they've managed to keep from the Dark Age of Technology, Humanity's lost Golden Age.
- Played straight in that most worlds completely lost contact with each other during a time known as the Age of Strife, and among other problems such as losing the knowledge and/or means to produce most high-tech equipment, developing completely different languages, or spending a few thousand years being the repeat targets of marauding Xenos, was the fact that most developed unique calendars. While some still maintain local, informal calendars - especially worlds whose year lengths differ drastically from Imperial norm - they're almost never brought up in fluff or official literature as having the official calender override everything else is part of the Imperium's attempt to "unify" all Mankind.
- Referenced in Grand Theft Auto: San Andreas. When a guy called The Truth gets something CJ stole from a government base, he says, "They shall call this Year 0."
- The Elder Scrolls universe has this happen at least three times.
- Or, depending on how strictly you look at this trope, twice (only two of the Era-transitions starts with disasters: the Second Era's assassination of the Reman Emperors and the Fourth Era's end of the Septim Dynasty).
- Both Xenogears and Xenosaga share the same in-universe calendar "Transcend Christ." It is identical to the Gregorian calendar, but it reset the year numbers so that AD 2510 is year one. A short time after the new calendar is chosen, humanity leaves Earth.
- In the Star Ocean games, the calendar was reset in 2091 so that 2087, the year of the invention of the first FTL engine, was year one. Dates are marked as 'SD' - spacedate.
- The Chrono Quake in the Galaxy Angel games.
- The Dragon Age series measures time against the establishment of the Andrastian Chantry and the crowning of the first Divine, with the current "age" (a period of one hundred years) used as an additional reference. Thus, something that occurred three years before that would have taken place in -3 Ancient (Age). Origins takes place in 9:30 Dragon (the 30th year of the Ninth Age, or "Dragon Age," 829 years after the crowning of the first Divine). The Tevinter Emperium measures time from its own establishment (TE), while the elves count the years from the founding of Arlathan (FA)—the ancient capital of the elves that has since been long wiped off the face of Thedas by the Tevinters.
- The world of Darien from Total Annihilation: Kingdoms measures time in years since the magical apocalypse caused by the Kandran Precursors, after which point civilisation had to be rebuilt from the ground up and all magic was banned.
- The EV Nova universe measures the New Calendar years against 2780 AD, the year FTL inventor Omata Kane died. At this point, a wave of offworld colonization began.
- The Warcraft series uses the "ADP" calendar, or "After Dark Portal." The portal itself was opened just before the first game in the series, so the calendar is fairly new; it's only been about 30 years in-universe. We know from the first game's manual that the year 1 ADP was the year 593 in the humans' old calendar, though given there are a good 14,000 years of history in the series it's unclear what event a mere 600 years ago caused another calendar reset.
- Analogue: A Hate Story has an unspecified drastic change in society on the spaceship, leading to a new year zero.
- The sequel, Hate Plus, explains that the reset was due to an armed rebellion that, while ultimately failing, resulted in the computer records being wiped.
- EverQuest II takes place in the year 500 A.K. After Kerafyrm. The awakening of an extremely powerful dragon named Kerafyrm in EverQuest set into motion a series of events that changed the face of Norrath forever, including deadly cataclysms that shifted the face of Norrath and broke up it's continents; the Second Rallosian War, in which the nigh-unstoppable Ogre army steamrolled their way across most of Antonica, only to be felled by divine intervention; and finally the destruction of the moon, Luclin, and the Lunar Armageddon that followed. Even for the Ogres themselves, they used their own calendar system during the war, because they signaled it as the beginning of a new empire that would control all of Norrath.
- Final Fantasy XIII-2 starts off in 3AF, or After (the) Fall (of Cocoon), three years after the end of the first game. Not only was everyone forced to start over entirely, leaving their past way of life behind, but time was literally warped as well, shaving the length of day down from twenty-six hours to twenty-four. Of course, it seems they also didn't really keep track before in the first place, with someone mentioning in the prequel novella that people from Cocoon don't even know exactly how long it's been since Cocoon was almost completely destroyed the first time.
- The world of Enroth in (the old universe, obviously) Might and Magic measured years in A.S — After the Silence. The Silence, in this case, is the year when Enroth lost contact with the Ancients. It is entirely possible that analogous calendars (just with different names for the Silence) was used on many other worlds, considering the Silence spanned an entire galactic arm.
- Runescape had the calender reset SIX TIMES. The First Age (World Creation); Second Age (Era of the Gods); Third Age (The Cataclysmic God Wars); Fourth Age (Rebuilding civilization); Fifth Age (Age of Man); and the penultimate Sixth Age (Return of the Gods).
- In Drowtales, when the vast majority of the elven race was driven underground, the entered a new age of their calender, 'The Moonless Age'. It has been 1100 years since and the kingdoms of drow now cover the underworld.
- The four "breakings" in The Dragon Doctors each started a new calendar. The current year is "625 4B".
- The Order of the Stick is set in the year 1183 (now 1184). The calendar appears to date from the creation of the world. (Or its recreation, as the original world was destroyed.)
- In Jack, the calender got hit so hard it restarted back to the Biblical Genesis.
- Homestuck: In the post-Scratch universe, as an alien takes over the world, her arrival is marked "0 Post Condescension", and years are counted from there.
- In Stand Still, Stay Silent the Known World set year the pandemia started as Year Zero, with New Year being in autumn. Events of the series start between year 90 and 91.
- Orion's Arm uses the Lunar calendar based on the landing of Apollo 11 in Tranquility basin (years denoted AT, After Tranquility), after the Nanodisaster and the evacuation of Old Earth.
- The two sequels to The Intercontinental Union of Disgusting Characters use years before and after the IUDC as their only system of datekeeping.
- The world of Shadowside marks the start of Evo's Dawn in A.E. 2007 with "P.E.D. 0". (Post-Evo's Dawn)
- Parodied in the post-apocalyptic Episode 10 of Knoxkast Radio, where Knox wonders if they should reset the calendar to Year 0. Jason instead decides to "do things differently this time" and declares that it is the year 8,036.
- The ancient Romans dated their calendar from the foundation of the city of Rome — Ab Urbe Condita or A.V.C.. Their original calendar divided the year into ten months: Martius (Mars(=Ares)'s (Mars being the god of war and farming, activities beginning in the spring)), Aprilis (Opening, i.e. of buds), Maius (Maia (a fertility goddess)'s), Iunius (Juno(=Hera)'s),note Quintilis (Fifth), Sextilis (Sixth), September (Seventh), October (Eighth), November (Ninth), and December (Tenth). When the ten month calendar proved unworkable, two new months were added at the end, Ianuarius (Opening or Janus's) and Februarius (Purification, referring to a winter festival). This change is attributed to Numa Pompilius, the legendary second king of Rome. In the 2nd century B.C., the beginning of the year was shifted from March to January in order to allow the newly-elected consuls to be ready for battle by the start of the campaigning season (spring).
- Gaius Julius Caesar, when reforming the calendar (and naming the whole system after himself) renamed Quintilis, the month in which he had been born, Iulius after himself, and Augustus renamed the following month Augustus after himself to commemorate the Battle of Actium. The Julian reforms primarily consisted of lengthening the existing months and doing away with the irregular "intercalary" months used to adjust the length of the previous system, which were subject to manipulation by the Pontifex Maximus, who was invariably deeply involved in Roman politics.
- Speaking of the consuls, the other (and more frequently used) major Roman dating method involved referring to a particular year as "[the year] X and Y being consul," which, naturally, was the year when the two individuals in question were consul. During one of Julius Caesar's consulates, his co-consul was such a pushover that people took to referring to that period as "Julius and Caesar being consul."
- A 6th century monk called Dionysius Exiguus ("Little Dennis") is believed to have been the first to have dated the calendar from the birth of Jesus of Nazareth; his calendar was popularized by its use in Bede's writings, leading to the B.C.note /A.D.note system most commonly used today. Dionysius's calculations, however, were criticized as inaccurate as early as the 12th centurynote , and were not universally adopted even in Christendom.
- In the 19th century, the use of B.C.E./C.E. (for "[Before] Common Era") was proposed instead, as a religion-neutral name for the same system. Adoption of the terminology has been mixed, but there's no denying that the system is the "common" one. ("We don't accept your religious beliefs, but damn does having one calendar for everyone make things so much simpler, and damn do you Europeans have one of the best calendars around."note )
- The shift from the Julian to the Gregorian calendars took place among Roman Catholics in the 16th century, but was not commonly adopted among non-Catholics until about the 18th note , leading to a difference of some eleven days. This is why some dates like George Washington's birthday will appear as February 11 (O.S.)note and February 22 (N.S.)note , and why Miguel de Cervantes and William Shakespeare died on the same date (April 23, 1616), eleven days apart. Russia held out into the early 20th century, not adopting the Gregorian calendar until after the communist revolution. Hence, the October Revolution actually took place in November. The Russian Orthodox Church still uses the Julian calendar, which is why Russians celebrate Christmas on January 7th.
- Many empires and kingdoms have changed calendars every time there was a new ruler, a concept referred to as regnal years.
- Although the United States doesn't use this in everyday business, formal Presidential proclamations will give years in both the Gregorian calendar year and the year of America's independence (which is, rather obviously, equal to the Gregorian year - 1776).
- This, as well as numerous gaps in written records, is why China's history is so maddeningly vague sometimes.
- Japan, still having an emperor, does it as well. 2014, for example, is Heisei 26. They use these alongside Common Era numbering, and it's common to hear people speak about dates in the Common Era only, as it's more manageable mentally.
- References to regnal years in the West are typically only seen in limited contexts with direct links to the monarchy; the most common one is probably references to regnal years in the Acts of the UK Parliament until 1963 (when they were replaced with Gregorian years) and Canadian Parliament to this day.
- The use of A.D. is, from a Christian point of view, a prime example of regnal-year numbering: Christ is the King of Kings, and since His first arrival on Earth, he has reigned for [current Gregorian year] years.
- Regnal dating, combined with the loss of historical records for entire periods of reign makes the Egyptian dynastic timeline a matter of extremely hot debate in Egyptology circles. While some gaps are simply due to the loss of records over time, others are due to various pharaohs purging the official records of any mention of their rivals or predecessors, and deliberately destroying or defacing monuments.
- During The French Revolution, not only did they restart the calendar, they made up an entire new month/week/day system. Didn't catch on. This was actually a little odd, as nearly every other unit the French revolutionaries came up with did catch on (they are collectively now known as the metric system)note Possibly metric time didn't catch on because it was unfamiliar (each day had ten metric hours and each hour had a hundred metric minutes) and the names of the months all changed, as well as being by far the most tied to revolutionary France. It also cut down rest days from one day in seven to one day in ten. Predictably, this wasn't popular with the mob.
- North Korea has the Juche calendar, with Juche 1 being 1912, the year of Kim Il Sung's birth. It did not replace (yet) the common world calendar but most North Korean publications include both dates. For instance, something published in 2013 will be dated "2013 / Juche 101".
- Taiwan has a similar system, which is based on 1911 (the establishment of the Republic of China) being Year 0. 2013 would be "the 102nd year of the republic".
- In Virginia, very formal state documents are likewise marked according to the common reckoning, and a "Year of the Commonwealth", with 1776 as Year Zero.
- Many formal documents like Law Degrees in the United States are stylized in the Year of Our Lord X, and of the Independence of the United States the n'th.
- When Pol Pot took control of Cambodia, he abolished the old calendar and declared the first year of his dictatorship to be Year Zero.
- In Fascist Italy, Roman numerals were used to denote the number of years since the establishment of the government in 1922.
- Veeery close to the definition of this trope is the Islamic calendar ("Hijri"), which started when Muhammad and his followers emigrated from Mecca to Madina. The enemies of the Meccan Muslims were about to assassinate Muhammad.
- Midnight on January 1, 1970, was chosen as "Second 0" to define the UNIX epoch. It was picked arbitrarily and not expected to be around for long, especially since we are going to run out of digits on January 19, 2038 (at 03:14:07 UTC), using the original method of storing that time (count one per second since the epoch: simple as can be; it's just they didn't anticipate UNIX surviving for over 2.1 billion seconds—the amount of seconds needed to go through 31 bits). Some newer systems have tried to fix this by doubling the size of the field used to store this information, so that the calendar will still work for eons and eons.
- The Church of Happyology dates its calendar from 1950 and the publication of "Dianetics".
- There is a small, perhaps insignificant, movement that holds the calendar should be reset so that Year Zero will be the year tvtropes.org came online.
- The Coptic Orthodox Church of Alexandria marks its time from 284 CE, the first year of the Emperor Diocletian. Why? Diocletian initiated the last Roman persecution of Christians, and since Egypt was pretty much majority-Christian by then, they felt the persecution particularly hard there—and so the era for the Coptic calendar is "Year of the Martyrs".