Universal Universe Time

Everything About Fiction You Never Wanted to Know.

"US Naval Observatory Master Clock. Eastern Standard Time, 2 hours, 1 minute, exactly. Universal time 7 hours, 1 minute, 5 seconds."

For a good time, call 202-762-1401 (613-745-1576 in Canada)

In most science fiction stories, although it is an issue that is seldom even touched upon, it appears that the entire Universe uses the same timekeeping and calendar system as Earth - years, months, weeks, days, hours, minutes, seconds, etc. Most planets also apparently experience a day/night cycle that is practically identical to that of Earth.

This is, of course, completely ignoring the fact that in the real world, the calendar and timekeeping methods we use here on Earth would, almost without a doubt, totally not work at all for 99.99999% of all the other planets in the universe. Because, surprise, surprise, planets orbit their stars at their own unique speeds, and they rotate on their axes at different rates, too, both of which are influenced by a large number of factors and can range from nearly static to extremely fast.

Just to put it in perspective for you: One "day" on Venus, our closest neighbor planet, is equivalent to approximately 117 Earth days because its rotation is so much slower than ours. On the other hand, one "year" on Venus is equivalent to 225 Earth days because Venus moves a bit faster, and its orbital path is shorter than Earth's.[1] It gets weirder – one Mercurian day is about 176 Earth days, or precisely two Mercurian years. (The precise 1:2 ratio is due to a 3:2 spin-orbit resonance.) Yes, that's right – on Mercury, a day is two years. (Feel free to speculate about whether dates like April p.m. have any meaning.)

When this occurs (even more bizarrely) in a Time Travel story, it's San Dimas Time and/or Meanwhile in the Future.

A Sub-Trope of Standard Time Units. Contrast Two of Your Earth Minutes, the standard Hand Wave to get around this.

Usually falls into the Acceptable Breaks From Reality category, because Most Writers Are Human. Sometimes Handwaved (or at least assumed by fans) to be a result of whatever makes us hear them in English.

To learn more, visit the analysis page.

Examples of Universal Universe Time include:

Anime and Manga

  • Averted in Aria, which takes place on a terraformed Mars called Aqua, they explicitly mention Aqua's longer year.
  • Crest of the Stars has at least one planet with an odd example. Since it was terraformed and opened for colonization by the space faring Abh they just used a single timezone with a 24 hour day that ignores the local day/night cycle, so 11 in the morning could be sunset, sunrise or the middle of the night depending on where on the planet you are.
  • Averted in Galaxy Express 999. It's an important plot point at times - the 999 stops for whatever constitutes a 'day' on each station's planet, and then leaves, missing passengers be damned. This is explained to the protagonist as early as the second episode of the series.
  • Apparently played straight in Legend of the Galactic Heroes, wherein the entire Milky Way Galaxy seems to operate on one standardized time zone.

Fan Works

  • Lampshaded in the Spirits Of The Force series of Star Wars fan films. In the second installment, Kyle asks Jan about the time, and Jan replies telling him the standard time on Coruscant. Then Kyle asks for current time. Jan looks back. Beat. "We're in space."


  • Avatar doesn't ever bring up the day and night weirdness that would come with living on a moon orbiting a gas giant in a binary star system. On the other hand, camera recordings display a date in day, month, and year in Earth time. Differences in the days, as well as the effects caused by the proximity to the gas giant Polyphemus on the day-night cycle has been addressed in both the wiki and the Activist's survival guide.
  • In Star Wars, the Galactic Republic (and the later Galactic Empire) uses a 368 day year calendar that uses the capital planet, Coruscant, as the standard, though mostly on Fleet ships and for the purpose of scheduling. Other notable deviation from our calendar includes a 5 day week and a 7 week month. Early EU material mentioned 10-month years, but this later became 12 for general understandability.
    • Because Faster Than Light travel is (near-) universally employed, special relativity is by-passed and Universal Universe Time is exactly what results. Apparently.
  • In Men in Black, they work on a 37-hour alien day, and a "week" is about an hour.
    • A galactic standard week is an hour, yes. But the 37-hour day is a specific alien culture's time system—presumably the first species MIB encountered.


  • Thoroughly averted in the Red Mars Trilogy by Kim Stanley Robinson, where the calendar requires some rethinking. The year is 669 days long (that's Martian days, by the way). The year is divided into twenty-four months, each 28 days long, with every eighth month being 27. They deal with this by using the name of every month twice, prefaced with 1 or 2 depending on which half of the year it is. They also measure the year in degrees for simplicity's sake, with the Spring Equinox being used for 0/360. The seasons are six months long. Oh, and Martian days are about 24 hours and 40 minutes. They don't bother reworking the timekeeping system though, they just stop the clock for forty minutes at midnight (they call this the "Timeslip").
    • This fails to take into account that Mars' highly elliptical orbit makes the length of seasons vary.
  • It's noticeably averted in Charles Stross' books Singularity Sky and Iron Sunrise, where it's acknowledged that FTL travel would make a form of time travel possible if a super-powerful AI didn't outlaw it.
    • In Accelerando by the same author, space travel within the solar system leads to a time system of seconds, kiloseconds (16 minutes, 40 seconds), megaseconds (11.57 days) and gigaseconds (31.7 years).
  • The Qeng Ho in Vernor Vinge's A Deepness in The Sky avert this by using a time system based on orders of magnitude of seconds. Still arguably applies, though, if only because their system is the standard universal one.
    • It also has its zero point set at the Unix epoch—00:00:00 UTC on 1 January 1970. In universe it's believed to date from the first lunar landing.
  • The Hegemony of Man from Dan Simmons' Hyperion Cantos uses a standardized day. Thanks to the Farcasters the time is the same everywhere in the galaxy at all times. When the protagonist ends up on the long lost Earth or maybe a recreation of it he's pleasantly surprised to find that the day night there happens to match one standard day, something he's never experienced before.
  • In Isaac Asimov's Foundation Series as "evidence" for the theory of humanity originating from one planet, when Earth is lost and forgotten. Not that everyone accepts this explanation for the length/number of hours, days and years.
  • The Honor Harrington series addresses this in a appendix to the first book. Every planet has its own clock and calendar, usually with a period after local midnight called compensation or 'comp' to deal with days not having a whole number of hours. Local years are divided up into (fairly arbitrary) number of months. Everyone uses Earth dates for international time-keeping, usually expressed as T-years, though in the Post-Diaspora calendar.
    • Except Grayson which, being colonized by an arch-traditionalist Luddite cult, uses Earth time units in spite of them being nowhere near suitable for the planet's rotational and orbital times. To top it off, they are the only culture that still uses A.D. to mean Anno Domini rather than Ante Diaspora.
    • More or less ignored as the series grows more complex and the Techno Babble is replaced with political intrigue.
  • Averted in the Vorkosigan Saga, where characters at least occasionally mention things like it being "18:00 hours of a 26.7 hour day [on this particular planet]".
  • Subverted in In Robert A. Heinlein's Stranger in a Strange Land: the main character, early in the book, notes to himself that the flow of time on Earth is different from his birthplace of Mars.
  • Played straight for the most part in Andrey Livadny's The History of the Galaxy books, where everyone in the Confederacy of Suns uses the same years. Months and days are, conveniently, almost never mentioned. The years are, of course, standard Earth years, even though Earth isn't even a part of the Confederacy thanks to The War of Earthly Aggression that led to the Earth Alliance being defeated by the Free Colonies, which re-formed into the Confederacy.
    • Subverted in one novel where an alien supercomputer asks how long it has been off-line, and a human replies that it has been over 3 million years, causing the computer to prompt for the definition of a "year". The human defines it as one full orbit around a star, prompting the computer to ask for further clarification as to the parameters of such an orbit. This stumps the human, as she has never thought of this. The computer then simply searches her mind and finds enough information about Earth to scan its own database for it. Of course, this fails to take into account that the database is 3 million years old, and Earth's orbit has changed since then.
  • The Dirigent Mercenary Corps series uses an interesting solution. They lengthen the second to make a Dirigentian day 24 hours.
  • Adverted in Embassytown by China Mieville where, given the number of planets colonized, time is mostly given in Kilohours. When the narrator does talk about years, they turn out to be about 3.5 earth years long.
  • John Varley's novel Red Lightning mostly takes place on Mars, which has a day that is 24.622 hours. The Martian settlers chose to make the day 24 hours by stopping the clock for the 0.662 hours.
  • Averted in E.E. "Doc" Smith's Skylark Three -- when a captured Fenachrone spills under interrogation that reinforcements will arrive in 'two-tenths of a standard period', the protagonist first has to loot a Fenachrone wristwatch and then do a lot of math to convert Fenachrone-minutes to hours to days to etc. just to find out how long a "standard period" (what we would call a 'year') is in their time system. Not surprisingly, it has absolutely no resemblance to a Terran year.

Live-Action TV

  • An egregious example on the Mystery Science Theater 3000-featured King Dinosaur: The scientists exploring planet Nova decide to use Earth time despite knowing that Nova's day-night cycle is likely different.
  • Star Trek averted it with their stardates, which were totally made-up with no regard to consistency between episodes. This is supposed to be because of differences in time dilation and related Techno Babble at whatever area the ship happens to be at.
    • Sometimes almost explained in the books, stardates generally are based around the rotation of the galaxy, as well as position in it. So depending on velocity (speed and direction) the stardate could go backwards. All told it's easier just to let it be wrong occasionally.
    • The real reason for stardates not being in order is that a) they were invented to avoid having to give a specific date on the calendar, and b) the episodes were not aired in the order they were produced. If you watch the episodes in the order they were made instead of the order they were first aired, the stardates are in order.
    • In Star Trek: The Next Generation and future spin-offs, the stardates got more consistent. Significantly, the second number of the stardate codes for the production season of the TV show, so 1000 stardates would approximate an Earth year. On the other hand within an episode, 1 stardate is usually a day so the time dilation must still factor in there somewhere. Additionally, the first digit (and most likely the second) and the decimal point represent the day and day fraction respectively
    • Slightly, very slightly averted in Star Trek: Deep Space Nine, in which it is reasonably frequently made clear that the station operates on a 26-hour day, based on the rotation of Bajor.
  • In Doctor Who, the Daleks measure time in "rels." One rel is slightly longer than a second, close enough to do the trick.
  • In Firefly, River points out that the use of "day" as a time measurement is obsolete, as they are part of a spacefaring civilization spread across hundreds of worlds. This is largely because she didn't get Simon anything for his birthday. Still, her view, like most of her views, appears to be unusual since everybody else celebrates Simon's birthday with no question (well, until the ship malfunctions and nearly kills everybody). Apparently, Earth time is still used for simplicity's sake.
  • Played with in Farscape. Rather than use Earth time measurements, they use space equivalents - an "arn" is an hour, a "microt" is a second, and (once or twice) a week is referred to as a "weeken". However, on many occasion someone will mention a length of time known as a "Solar Day" - which is supposed to be one day. This may seem odd considering nobody on the show (short of the main character) has ever even heard of Earth and the term "Solar" refers to Earth's sun, Sol.
    • Not so weird when you remember that in the first episode it is explained that Crichton's been implanted with a Universal Translator which makes him perceive all of the alien languages as being in his own native tongue. Meaning that if "Solar" is the best translation of the concept in English, then "Solar" is exactly what Crichton will hear.
  • The original Battlestar Galactica did much the same thing. The best-known example of that was the "yahren" or year-equivalent, but there were several others that served as counterparts to seconds, minutes, hours, weeks, etc. (though a day seemed to be a day regardless). Unfortunately, the writers seemed to get confused as to what Colonial Unit meant what, which led to it being hard to tell if "microns" and "centons" were units of time or units of length. Fans have tried to get round this by saying that it was common practice to refer to a "light-micron" as just a micron, but actual series canon gives no support for this.

Tabletop Games

  • Carefully averted in Warhammer 40,000, where a universal dating system based on an Earth year is used by the Administratum, but it is purely for administrative purposes and individual planets generally adhere to their own calendars.
    • It's one of very few dating systems with a built-in tolerance for the difficulties and delays of interstellar communication. The first digit of the date specifies the accuracy compared to Earth. a 0 (or a 1) indicates a date on Earth or within the Sol system, a 2 indicates a date somewhere in direct contact with Earth, a 3 indicates a date in direct contact with somewhere in direct contact with Earth and so on. 6, 7 and 8 are used for when the event happened during a period where the place it occurred was out of contact, with increasing degrees of inaccuracy. 9 means the date is wholly conjectural (based on carbon dating, or derived by inference from legends) or converted from a non-standard date system.
  • Possibly not a valid example, but in Exalted, the yearly calendar consists of five seasons, with three months each, five weeks to a month, and seven days to a week, all of them matching perfectly with the solar and lunar cycles. Oh, and there's a five day period between years called Calibration, during which things can get very, very strange indeed.

Video Games

  • Briefly seen but never explored in Free Space 2. When serving on a Terran vessel, all times are given in the familiar GST format, but on Vasudan ships, Vasudan time is used, which leads to a certain incident being described as occuring at "68:32 Vasudan Standard Time."
  • Mass Effect appears to play this straight. The second game takes place two years after the first - this figure is given by any character regardless of species or what world he or she is on though this might be partially a result of the universal aural translator's translation.
    • Explained in the Expanded Universe; the Council created a separate arbitrary Galactic Standard time for the galaxy that isn't based on any single planet specifically to coordinate everyone.
      • And the Standard time is not exactly, but close enough to human time that people use them interchangeably. Alternatively, as Shepard has been in the military for years, it's quite possible the references to years are actually to the Galactic Standard and not Earth years. The game offers all three possibilities but never gives a definitive answer
      • It may also simply be convenience or even Translation Convention (everyone is either speaking their own language translated into English by tech or Galactic). When Liara tells you that she has been mourning for two years, for example, she may simply be converting her Asari time into Earth time for the sake of politeness, or the Translation Convention renders "I have been mourning you for seventeen zlargs" (or whatever Asari call years/months) as "two years."
    • Averted elsewhere. Each selectable planet has a description, and none of them has anything approaching an Earth day/year. Also, the human in Eternity on Illium mentions that "salarian years are like dog years."
    • Averted in the case of an advertisement on the Citadel's Zakaera Ward - it gives a date in human time (because the advertisement recognizes Shepard as a human) but in such as way as to make plain that there is a wide variety of galactic time and date systems:

Advertisement: This is a public notice that Citadel Security will be holding an auction of confiscated property in this Ward on: [*pause, followed by obviously separate recording] Earthdate: August 4, 2185 at 08:30 Zulu time. Items to be sold include jewelry, personal electronics, private starships, cargo and sport related personal shuttles, art and antiques from various cultures. For more information visit any C-Sec kiosk, or link into Citadel Net at keywords: C-Sec, auctions, Zakaera.

  • An interesting variation occurs in Super Robot Wars Judgment, where the Lunar Furies apparently measure time in galactic days, i.e. the time it takes the entire Milky Way to complete one full rotation. One of their days is roughly several million of our years.
  • Justified in the X universe, which features not only interstellar travel but individual ships undergoing time compression. Instead of seconds and minutes, time is measured in sezuras and mizuras or Universal Coordinated Time, values measured from observations of a specific pulsar, and the synchronized 'now' a habit created by the Portal Network trade lanes.

Web Comics

  • In Darths and Droids, Qui-Gon Jin finally dies by rolling a 1 to stabilize. The DM tries to explain that he can use Fate Manipulation to reroll, since a day had passed. But, being two nerds, Obi-Wan and Qui-Gon talk him out of it be arguing that what is a day since they spent the "night" in space. Is 24 hours a day on Naboo? Or what? Of course, the DM then just says, screw it, you died. At which point they are both happy they won the argument... then realize the prize.
  • Starslip averts this when the main character declares he sets his clock by whichever star he's closest to, which in real life would actually be pretty difficult ("I'm late for my appointment at 6! Thousand!").
  • Unity uses its own ship-local time, based on sec, kaysec (1000 secs), deci (10 kaysecs), day (10 decis), dec (5 days), and round (5 decs). They also consider a tenround (10 rounds) as a standard-ish unit of temporal demarcation. The actual calendar is just a decimal count (1.000 = 1 day) based on some arbitrary time period without any in-ship time zones, as relative intervals are more important than absolute points in time. Absolutely no attempt is made at dealing with external time references, but without any FTL travel or communication, there's no need for it either. And, the day of the dec is simply the current day value modulo 5; the days are, thus, called "onesday," "twosday," "threesday," "foursday," and "fivesday."

Web Original

  • In Orion's Arm people have given up on trying to establish any such system, even with the help of wormholes.

Western Animation

  • Tripping the Rift.
  • Transformers in general plays around with the wording. Whether or not they follow Earth's calendar and time standards is never really expressed, but they use phrases like "One Solar Cycle" to represent 1 day or a Mega Cycle to represent a month (or possibly a year.)
    • The comic books talk about vorns and such, and they add up to a sufficiently random number of Earth years. However, the result is, if you didn't write down how long each unit of time was last time it was told, having no idea how long they're talking about when breems and vorns and joors and such come up.

Real Life

  • Truth in Television, go far North or South enough here on Earth and a day is suddenly no longer than 24 hours.
    • Day isn't 24 hours anywhere but on the poles if you're talking about the period in which you can see the daylight. If you're talking about the abstract measurement from midnight to midnight, it's 24 hours everywhere on the planet.
    • Antarctic bases tend to use the time zone of the places their supply flights take off from. So some of them use daylight saving during the months in which the sun never sets.
  • GPS satellites are so precise that they have to compensate for both the effects of Special (due to the satellite's velocity around the Earth in orbit) and General Relativity (because the Earth is deeper in a gravity well than the satellites).
  • The Darian calendar is a proposed calendar for Mars. It has already attracted controversy from various religious authorities; dates on the calendar occur on the same day of the week year after year because 27-day months skip from Friday to Sunday at the end of the month. This, however, means that the Abrahamic day of rest migrates around the week instead, interfering with the work week.
    • When working with remote landers on the Martian surface, especially those powered by solar collectors, NASA has a vested interest in knowing whether the sun is up or not. Mars missions, therefore, operate on a series of "Sols", which is their shorthand name for the Martial solar day. Some of the folks working on these missions even wear wristwatches calibrated in Martian time, often set for the local "time zone" on Mars where the lander currently is.
  • Nobody has developed a calendar for Venus yet, due to its unusually long day compared with its year. However, one possible method of colonizing Venus would be using floating cities that would ride winds that circle the planet every 4 days. This would make it more plausible for colonists to use Earth-length days, with the Venusian year (~224 Earth days) conveniently divided into 8 months of 28 days each.
  1. The 243 Earth days figure you may see bandied about as the length of a Venusian day is its sidereal day. The mean solar day is shorter due to Venus's retrograde rotation, whereas planets that rotate prograde have a solar day that is longer than the sidereal day.