The Hidden Hour (a.k.a. the Witching Hour) is a period of time within the average day that is Invisible to Normals; most people don't experience it, nor are they aware it even exists at all. Only a few people, often those with some kind of special power, know about this extra hour; and only they are able to act during it. To these people, when The Hidden Hour occurs, normal clocks stop ticking, Muggles freeze in place (or vanish entirely), and strange things start to happen.
The Hidden Hour frequently occurs When the Clock Strikes Twelve, due to the association between midnight and magic. However, this is not about magic simply being at its strongest around midnight, nor is it about planets whose day-night cycles are naturally longer than 24 Earth hours.
It's interesting to note that an extra hour added to a twelve-hour clock would be the thirteenth hour. You've got to ignore the fact that there are really 24 hours in a day for this to work, but numerology has never been shy about fudging things for the sake of Rule of Drama...
In spite of the name, The Hidden Hour is not necessarily 60 minutes long; it frequently lasts as long as the plot requires, which to those involved may feel like several hours, or possibly even days, before the Hidden Hour ends and normal time resumes.
- There's a short manga called Crossing 25, in which the 25th hour is inhabited only by a handful of people who fight over whether tomorrow will arrive or not.
- Dark City has something along these lines, with everybody just falling asleep on the spot at the appropriate time. Fortunately, all cars and trains in the movie seem to have "Sleeping Man Switches" to keep them from plowing into things or each other.
- In Labyrinth, Sarah is taken to Jareth's world late in the night and spend 13 hours there, before returning at midnight and Jareth uses a 13 hour clock throughout the film.
- The Midnighters Trilogy has the Blue Time, between midnight and 12:01, though in the last book it starts appearing during the day as well. Also involves monsters which attack the defenseless ordinary people (or would were it not for the efforts of a bunch of teenagers who fight them with superpowers and the number 13).
- The book Tom's Midnight Garden has Tom able to access the titular garden via Time Travel when the clock in his aunt's house strikes 13 at midnight.
- Philip José Farmer's Dayworld books have a slightly more science-fictional version of this. To combat overpopulation, just about everyone is in stasis six days out of seven, and there's a half-hour gap between the time one day's population goes into stasis and the time the next day's population comes out.
- The science fiction story "Zeepsday" by Gordon R. Dickson is about an alien race that shows humanity that there is an eighth day in the week.
- Clive Barker's Abarat Trilogy deals with a magical archipelago where each hour of the day is represented by an island. There is a 25th island, that remains highly mysterious even after it's visited.
- The Eleven-Day Empire, from the Doctor Who Expanded Universe, was created from the 'missing' days between 3 and 13 September 1752.
- The entire plot of Stephen King's short story The Langoliers from Four Past Midnight. Several people wake up on an airplane mid-flight to find themselves all alone in the world and trapped in a sort of garbage space between days, where the entire world is erased and created anew.
- In R. A. Lafferty's Days of Grass, Days of Straw heroes take it upon themselves to wrestle with the gods; if they win, the human race is allowed a "day of grass", when all of life is more intense and fulfilling than the "days of straw" that constitute everyday life. (We don't remember the days of grass during the days of straw, although deja vu, love at first sight and such phenomena are caused by a sort of half-memory of people we met and things we did in those happy moments.)
- A rare non-magical examples occurs in Kim Stanley Robinson's Red Mars Trilogy: on Mars, the day is 40 minutes longer than on Earth, and they deal with it by freezing the clock each night at midnight. The 40 minutes becomes a sort of free time, a time that is considered not to really count.
- The Twilight Zone (1985):
- In the episode "A Matter of Minutes", based on Theodore Sturgeon's short story "Yesterday Was Monday", a couple are caught in a space with no time where the future is being constructed for each minute.
- The same series also has "Paladin of the Lost Hour", where there's a secret hour contained in a pocketwatch and only revealed to one person at a time, but it's a borderline example since the hour never actually occurs (if it did, the world would end).
- Stargate SG-1 had the main characters effectively experience one of these. They were on a planet where people were linked into a computer system. Every so often, the computer would "pause" everyone. During this time, the team walked around while the population was frozen.
- In an episode of Eerie, Indiana, after being told that Indiana doesn't observe Daylight Savings Time, Marshall sets his watch back an hour anyway, wanting to get the extra time. He wakes up an an extra hour inhabited by lost children and milkmen.
- "25 O'Clock" by The Dukes of Stratosphear.
- Don't Rest Your Head has a hidden hour that occurs twice a day, once at noon and once at midnight.
- However, this extra hour occurs only in the Mad City; no-one in the real world, supernatural or not, experiences it. As a result, people in Mad City cannot enter the real world during that hour.
- During this time, all players play with hole cards in Hoyle's Rules of Dragon Poker.
- Persona 3 has the Dark Hour, between midnight and 12:01 a.m., wherein monstrous Shadows, based off the ideas of Carl Jung, roam free and ordinary people turn into coffins.
- Terranigma the opening sequence makes reference to the clock having 13 hours, which leads to an important plot point later.
- Billy vs. SNAKEMAN has The Dark Hour as part of the Monochrome Academy questline; the hour cannot be detected by normal people, and it's when the dark forces occupying the school (including Mister Tea, who was presumed dead) come out to do battle. Once you've passed the Dark Hour quest, certain hours of the day (thankfully conventional ones that fit into normal space-time) are listed as "Dark Hours", and you can compete in the Arena against other Dark Hour players. The Pizzawitch questline also has "The Witching Hour", where you can race in certain extremely difficult Fields that only become available at this time.
- Aeon from Castlevania: Judgment is a time guardian whose powers revolve around time and clocks. Notably, his clock has thirteen hours on it.
- SCP Foundation has Liberary, an entire period of 47 days that doesn't exist in normal time. No one remembers the events of Liberary once it ends, but every Liberary people regain their memories of all the previous Liberarys. It causes people to relax their inhibitions and basically engage in a month-long hedonistic celebration. It also nullifies The Masquerade for its duration.
- Zig-zagged by Daylight Saving Time, or Summer Time. Transition to DST implies moving clocks one hour forward (usually in the Saturday-Sunday night at 0200 AM) and return to winter time implies moving them back one hour. It is basically having one hidden hour in the Spring and sensing one hidden hour in Autumn.