Microts

"Kryten: Hmm yes, he's giving us 5 hanaka to decide. Rimmer: How long's a hanaka? Kryten: Curiously enough it's exactly the same as one Earth minute. Cat: 5 hanaka! That only gives us 28 hours."

- Red Dwarf, Emohawk

Fictional universes call for fictional measurements of time. After all, why would an alien culture use the same words for time as an Earth-based culture?

Strangely, 'alien' time units correlate pretty well with Earth time units in the majority of cases. 'Cycle' is the most common of these, usually referring to a year (though sometimes a day).

This can be justified easily enough; aliens probably live on a planet that orbits a star and has a day-night cycle, so they might well have natural units of time corresponding to "day" and "year," though probably not exactly the same length (unless, of course, the planet in question is almost identical to Earth and the star it circles is the same as the Sun, in which case it may be the same distance away and would therefore have about the same length for a year. No accounting for days, though.)

If an alien character doesn't use their own measurements, but instead uses Earth measurements in a jarring manner, they're talking in terms of Two of Your Earth Minutes. If these units are used across multiple worlds or civilizations, they are Standard Time Units. See also Fantastic Measurement System for other fictional units.

Comic Books

 * The Marvel Transformers Generation 1 comic book series introduced two Cybertronian time units: a "Breem" (8.3 minutes) and a "Vorn" (83 years). Apparently, giant shape-shifting robots never bothered with units of time greater than 8.3 minutes and less than 83 years...
 * There are also 'orns', with an 'orn' being 'one Cybertronian lunar day'. Which isn't all that helpful, as we're never told how long that lunar day is.
 * That doesn't even begin to do justice to the silliness of Cybertronian units.
 * In the Bronze Age, Superman comics stated that Kryptonian time was divided into "dendars", their equivalent of a minute that consists of one hundred seconds, which implies that Kryptonians were very enthusiastic about the metric system.
 * The recent New Krypton story arc in Superman has the Kryptonians using a weird time unit, apparently of an order of magnitude similar to the minute.

Fan Works

 * The time system in Ketafa in With Strings Attached is some strange thing divided into five big chunks, four sets of five smaller chunks, and 400 smaller units. Times are called, very prosaically, “2-3” or “5-5” or whatever. The four never bother to find out anything about it.

Film
"Kay: Arquillian battle rules, kid: first we get an ultimatum, then a warning shot, then we have a galactic standard week to respond. Jay: A "galactic standard week?" How the hell long is that? Zed: One hour."
 * Men in Black uses this trope in a grimly comedic way, tossing 'week' in where it really shouldn't go...

Literature

 * Inverted in The Wheel of Time, where a ten-day period is called a week. This is mentioned exactly once in the story, in an offhand mention going something like, "Four more two-day festivals scheduled for this week," leading the casual, non-glossary-reading reader to believe that Robert Jordan was an idiot.
 * Many fans have been confused by the combination of the above and Moiraine's conversation with Nynaeve about when she began channelling, where she asks if Nynaeve experienced certain things in "a week or ten days." So apparently she meant "a week, i.e. ten days".
 * In Steven Brust's Dragaera novels, a Dragaeran week is 5 days. Humans/Easterners still use seven-day weeks, and even fortnights (14 days), which Vlad (raised in Dragaera) thinks is a really weird period of time to have a name for because it is "...one day shorter than three weeks."
 * Most of L.E. Modesitt's novels, even those in entirely different settings, have "eightdays" instead of weeks and use "kays" for distance.
 * Edgar Rice Burroughs' Barsoom stories. Martian civilization used the following time units: 1 Xat = 200 tals, 50 xats = 1 zode, and 10 zodes = 1 Martian day. Mars has a day almost identical to Earth (24 hours 37 minutes), so 1 zode = 2 hours 28 minutes, 1 xat = 3 minutes and 1 tal = .9 second.
 * Gor (based a lot on Barsoom) measures 80 Ihn (seconds) to the Ehn, 40 Ehn (minutes) to the Ahn, and 20 Ahn (hours) to the day.
 * Mercedes Lackey's books that take place in Valdemar call an hour a "candlemark". In her Obsidian Trilogy, characters from a certain city reckon time in units of "bells", each of which is two hours.
 * The whole "candlemark" thing comes from a real-word form of clock from the medieval period, which was simply a candle made in a length which would (theoretically) take X hours to burn down. The candle was striped in hour-long segments, so you could tell by looking at it how long it had been since you lit it. Obviously there was much potential for imprecision in the real world; in Valdemar they've got it down to a bit more of a science.
 * The Race in Harry Turtledove's Worldwar series apparently operates on metric time, as their phrase "one tenth of a daytenth" equals out to about fifteen minutes.
 * The giant, moving city on rails in The Inverted World uses "miles" as a measure of time. Though initially confusing, this is eventually explained when it is revealed that the City has to move 1/10 of a mile per day in order to survive; thus, a character might say "a mile ago" to mean "ten days ago".
 * In Isaac Asimov's Robot City series (by Rob Chilson, William F. Wu, Arthur Byron Cover, Michael P. Kube-McDowell and Mike McQuay) the robots use normal time units, but since the days in the titular city are of a different length, the human heroes get metric watches dividing the day into decades and centades.
 * Often used in the Star Trek Novel Verse. For example, 6 human months equals about 4 Vostigye ronds, and nearly 40 Talaxian niziks. A Romulan Veraku is about 63 Earth minutes, and a Siuren is roughly 50 seconds.
 * At one point in the Dragonback series, Alison Kayna notices that the Valahguan "Death" weapons the scout fleet gets hit with cut off after three minutes and 47 seconds, which led her (correctly) to the conclusion that the weapons were strictly a loaner and that the enemy alliance wasn't that firm. Draycos mentions that that would fit, since 3 minutes 47 seconds works out to two birs of Valahguan time measurement.
 * A "week" on Discworld is eight days long. This could, potentially, have caused difficulties with the Discworld Diaries line of humorous datebooks, but the quandry was resolved by saving Octeday for amusing anecdotes and character sketches.
 * It is also canonically established that a year (a full revolution of the Disc) is 800 days and has eight seasons. This is never respected after being established, so a linked system of “short years” of 400 days and 4 systems was retconned in. If you’re going forward along the turtle’s left side in summer in an odd short year, you’ll be going backwards on the right side in an even summer. To keep things simple, each short year has 13 months.
 * In Joan Vinge's The Outcasts Of Heaven Belt, all time units have been replaced by multiples of seconds (megaseconds,gigaseconds), freeing them from dependence on any local rotation or revolution cycles.
 * In the Darkover books, a Darkover day is twenty-eight hours. Why twenty-eight? Presumably (in the author's attempt to retcon this), the original Lost Colony approximated the Earth hour (before they forgot their origin), but adjusted to a new day length.

Live Action TV

 * Trope Namer Farscape's alien characters commonly use 'microt', 'arn' and 'cycle' in place of 'second', 'hour' and 'year' (roughly). John Crichton (the only Earth character in the series) picks up on it, and often counters with nonsense of his own.
 * Microts seem to alternate between seconds and minutes, depending on the needs of the story.
 * I believe Microts, Arns and Cycles are another iffy thing of the translator microbes, like cursing, where the microbes translate the word to a close enough meaning as mathematical measurements such as time and distance would have no real relation to each other, as a different planet has a different length day.
 * Or microts are used figuratively, as is done with seconds in English. When someone says "Gimme a second" he or she is not literally asking for one solitary second, but rather a moment's time.
 * In the early episodes, their usage of units varies a bit. However, by the first third or so of the first season, they're pretty firmly established. A microt is roughly a second (180 microts = 4 minutes = 240 seconds; 1.3 seconds per microt), an arn is roughly an hour, a "solar day" is roughly a day, a weegen (only used once, by D'Argo) is roughly a week, and a cycle is roughly a year. A metra is on the same order of magnitude as a kilometer and a motra is on the same order of magnitude as a meter. "Square dench" (square inch?) and "milon" (mile?) are also used, though rarely. See? Easy!
 * The original 1979 Battlestar Galactica series used "microns" for seconds, "centons" for minutes (or for hours in the series pilot), "centars" for hours, "sectons" for weeks, and "yahrens" for years.
 * "Yahren" is pronounced exactly like the German Jahren, the dative form of the word Jahre meaning "years". In fact, the plural of "yahren" in old BSG was "yahren". So yes, BSG did just rip off German.
 * In real life, "micron" is slang for micrometre, is one-thousandth of a millimetre, but that would mean that when the Cylon raiders were "ninety microns and closing," they were 0.09 mm away. But seriously, folks, the Viper coordinator probably meant the raiders would arrive in 90 seconds on their present course and speed.
 * The show hung a Lampshade on it in the episode Greetings From Earth where other human space colonists used seconds, minutes, and hours while Apollo said "Wait just a centon!" trying to figure it out.
 * Re-imagined Battlestar Galactica averts this, except for some documents visible onscreen in Armistice Station in the Miniseries, which use original-series terminology. Spoken dialogue and other writings have "years", "minutes", etc.
 * In Doctor Who, Daleks use "rels" to indicate a short period of time, which varies between about one and two seconds from one episode to another.
 * Time Lords in the Expanded Universe measure time in spans and microspans.
 * In Babylon 5, Drazi cycle not Drazi week. Cycle Drazi year. It can be assumed that almost all species have their own time units, but the Babylon station runs on Earth time.
 * Some early episodes referred to on-station time in terms of "cycles", but this was dropped in favor of standard Earth time units.
 * Starting with Star Trek III: The Search For Spock and continuing on at least one episode of Star Trek: The Next Generation, Klingon Battlecuiser crews call out the distance to their targets in "Kellecams". (Or "killicams". Or "kilicams". There doesn't seem to be much agreement on the spelling. As they're translating from Klingon, the closest would probably be something like qelI'qam.)
 * Beginning with Star Trek: The Next Generation, stardates were (sort of) standardized to a year being 1,000 units long, with each unit being subdivided into 10 subunits. That would mean that 1 unit is equal to roughly 8 hours, a subunit is roughly 48 minutes, while a day is 3 units. Thus, the launch date of the Enterprise-D, stardate 41153.7, correlates to February 20, 2364 at 5:36 am.
 * The planet in the Star Trek: Voyager episode “Time and Again” used rotations, intervals, and fractions. And western Arabic digits (that's 1 2 3, not eastern Arabic ١ ٢ ٣).

Tabletop Games

 * Exalted has a year... that's made up of 15 months and 5 days that are "outside the year", called Calibration. Also, the month is made of exactly 28 days, no matter what month it is, unlike our months. (makes sense, since they use lunar months, unlike us who use Roman months and calendar, where every Roman emperor wanted a month dedicated to himself and wanted that month to be longer than normal. Which leads to July and August having 31 days, while poor February is left with merely 28 (ok, 28.25)...)
 * The Forgotten Realms has the "tenday", which some nations call a "ride." Hilarity sometimes ensues due to confusion, when a person says "two rides" and listeners think they mean two days of riding.
 * Paranoia supplement Acute Paranoia. Alpha Complex used the phrase "half a cycle" for the period between 1 wake-up call and the next (i.e. 1 day). A "cycle" was therefore 2 days.

Video Games

 * The X series has the "sezura", "mizura", "tezura", "wozura", "mazura" and "jazura". Bet you can't guess what those correspond to.
 * Actually, none of them directly correspond to Earth time units. 1 sezura = 1.7 seconds, 1 mizura = 96 sezuras (2 min, 43 sec), and continuing into ever more irregular measurements.
 * The Slylandro in Star Control 2 have "rotation," "Drahnasa," and "Drahn" which are something like their equivalent of days, years, and millennia (not particularly similar in duration to ours though). It would be tricky to decode these except that pretty much everything interesting that's happened on a galactic scale happens in one of three time periods (Quite Recently, A Long Time Ago and A Really, Really Long Time Ago) so luckily it's not too hard to figure out what they're on about.
 * To be more precise, one "rotation" is one "day" of their planet, 1 Drahn is equal to 4 million rotations and one Drahn is divided into two thousand Drahnasa. Some code examination reveals that the rotation of the Slylandro homeplanet is 14.2 earth hours which tells us that one Drahnasa is equal to 1180 earth days and one Drahn is 2370000 earth days.
 * The people of the Metroid universe use "cycles" for a span of time somewhere between a few months and about a year. Space Pirate logs often talk about projects being developed over the course of a few cycles, for example figuring out how to infuse their troops with Phazon, especially as it took multiple failed attempts. U'mos in Metroid Prime 2 is mentioned to be several centicycles old (technically it should be centocycles, but that's a different trope entirely). Might it be some based on other planet's year?
 * The Komato and Tasen use "cycles", "pulsecycles", and "starturns", although how they correspond to human units of time is unknown. Starturns would presumably be a Komato year, but since we don't know how long it takes their planet to orbit, it doesn't help much.

Web Comics

 * In The Inexplicable Adventures of Bob, the dragons and Nemesites measure time in "zarps." Since "half a zarp" seems to equal at least a short night's sleep, we can guess a full zarp is probably something between 12 and 16 hours. An author's comment when they first appear compares them to astroseconds, centons, and rels.
 * The trolls in Homestuck call years "sweeps", although the Alternian year is equal to around 2.17 Earth years.
 * In Escape from Terra most Belters use a decimalized calendar and time-keeping system designed by the Mars colonists. Particularly "centimes" (about 14.8 minutes, if my math is correct) and "decadays" (10 Martian days).
 * In Last Res0rt the galaxy has apparently adopted Swatch Internet Time

Western Animation

 * In Teenage Mutant Ninja Turtles, Donatello calculates a ratio of 1 Triceraton trigon to 10 minutes.
 * In Beast Wars: Transformers, 'cycles' are used for minute-like timespans. There are also "nano-kliks" (roughly a second), "decacycles," "megacycles," and "stellar cycles," which varied Depending on the Writer (megacycles at one point going from roughly an hour to, from context, roughly a year).
 * Transformers Animated uses this so much you really wish they'd just break down and convert the damn units. "Wait a cycle!" "I haven't done this in deca-cycles!" "I have bided my time for eighty mega-cycles..."
 * The original Transformers series had the infamous "astroseconds," "astrominutes," "astrolitres," "a Cybertronic mili-inch," etc. The first episode mentioned a unit of time called a "quartex," but it was never mentioned again.

Real Life
"Zed: The twins keep us on Centaurian time, standard thirty-seven hour day. Give it a few months. You'll get used to it. Or you'll have a psychotic episode."
 * Historically, attempts to replace seven-day weeks with something else have failed. This has been attributed to, of all things, bearded men preferring to trim their facial hair on the same day each week: wait longer than seven days and it grows enough to get tangled; don't wait as long, and they're grooming themselves before there's much need to do so.
 * The Metric calendar failed in part because pretty much everyone (this was revolution-era France) still had to use the old calendar to track the Sundays. A calendar change also causes problems for holidays like Easter, the date of which is based on the interface between a seven-day week and the lunar cycle and moves every year.
 * When NASA scientists are talking in terms of subjective time on another planet, they use "sols" to cover a single rotation of the planet, to keep the Earth measurements lined up with the clock. The Martian sol is 2.7% longer than an Earth day, so the difference is about 40 minutes a day. This can really add up over the months and years. Since all on-site equipment is solar powered, all scheduling is done according to the length of sols, and some team members have Martian time watches. Some particularly dedicated researchers end up having rather peculiar sleep schedules by Earth standards.
 * Martian time isn't that bad; the 24-hour-40-minute day will let you keep a reasonably stable sleep cycle that's consistent with the rhythms of the human body. Heaven help you if you were dealing with a planet that has 16-hour or 30-hour days, though...
 * Another Men in Black joke:


 * In 1969 the Swiss company Helbros brought out a "lunar watch" for the use of astronauts, which divides the lunation into 30 "lunes" of 24 "lunours". (Centilunours and decilunours for shorter periods.)
 * Various forms of decimal divisions of the day.
 * The Other Wiki lists several unusual time units, such as the 1.2096 second "microfortnight".
 * An in-joke in the Arch Linux community are kiloseconds.
 * Combining the above, note that a "millifortnight" comes out to 1,209.6 seconds, i.e., very close to 20 minutes, or a third of an hour.
 * Many native American folk myths begin with the phrase, "Many moons ago." One "moon," of course, was the time from one full moon to the next, or from one new moon to the next, which is about (but not exactly) a modern calendar month.
 * To be precise, it's 28 days. Approximately. (But closer to 28 than to 27 or 29.)
 * Most people don't know that "moment" is actually a strictly-defined unit of time from the Middle Ages: there were 40 moments in a solar hour, which itself was defined as one twelfth of the period between sunrise and sunset.  Naturally, since this period varies day-to-day and season-to-season, the medieval moment had no fixed duration, but some modern interpretations set it at one-fortieth of a modern hour, or 90 seconds.
 * Just in case you're curious, the medieval system was even more complicated. According to the Venerable Bede, a solar hour could be broken down into 4 points, 10 minutes or 15 parts as well as 40 moments; i.e., 10 moments = 1 point, 4 moments = 1 minute and so on. And eventually the moment itself was subdivided into 60 ostents.  The actual durations of all of these units varied by time of year, of course, and some were little more than theoretical oddities, unable to be measured at all with the equipment available at the time.