Stardates

Stardates are a fictional alternative to calendar dates in the Star Trek TV series, movies and books.  They are typically represented as a four or five-digit number with a decimal point followed by one digit, such as 1234.5.  Several distinct versions have been used by the various series and movies.  (Star Trek: Enterprise was set in the 22nd century, prior to the other series, and did not use stardates.)

Timeline

 SeriesStardateYear1Released
22rd Century
EnterpriseNone21512001-09-26
None21552005-05-13
23rd Century
Movies 11 122258.4222582009-05-08
2259.5522592013-05-17
The Original Series1312.422651966-09-22
5943.922691969-03-14
The Animated Series1254.422691973-10-27
7403.622701974-09-14
Movies 1 2 3 4 5 67412.622721979-09-07
9521.622931991-12-06
24th Century
The Next Generation41153.723641987-09-28
47988.023701994-05-23
Deep Space Nine46379.123691993-01-03
52861.323751999-05-26
Voyager48315.623711995-01-16
54973.423782001-05-23
Movies 7 8 9 1048650.123711994-11-18
56844.923792002-12-13
1 From Star Trek Chronology

The original series (TOS)


The original Star Trek TV series aired for three years in the 1960s.  There were also six motion pictures with the original cast, and an animated series and numerous books.  TOS stardates were four digits followed by one decimal.  There was no correlation between stardates and calendar dates, except that they generally increased in time during the series.  The decimal digit was supposed to represent decimal time. According to The Star Trek Guide, the official writers guide for the series:
For example, 1313.5 is twelve o'clock noon of one day and 1314.5 would be noon of the next day. Each percentage point (sic) is roughly equivalent to one-tenth of one day.
The time period was never stated in the series. The episode "Space Seed" states that it is two centuries after the 1990s and other episodes suggest other time periods, and it was often assumed to have occurred in the early 23rd century, but the movie Star Trek IV: The Voyage Home later stated that it takes place in the late 23rd century, and Star Trek Chronology and later canon established more precisely that TOS was set about 300 years after it aired, in the 2260s.

Alternate Reality

An alternate reality in the Star Trek universe was created in 2009, when a new movie franchise was started with the TOS characters and an all new cast in the movie Star Trek.  It also introduced an all new type of stardates, which is simpler and based upon year numbers in the Common Era.  These stardates are simply the current four digit year, followed by a decimal representing the ordinal day of year. Two stardates are given in the the 2009 movie, 2233.04 (when Kirk is born) and 2258.42, corresponding to January 4, 2233, and February 11, 2258, respectively.  The next movie, Star Trek Into Darkness, was released in May of 2013, and begins on stardate 2259.55, i.e. February of 2259.

The Next Generation (TNG)


Star Trek: The Next Generation aired for seven seasons in the 1980s and 1990s, and was set about one hundred years after the original series, in the 24th century.  It was followed by two spin-off series, Star Trek: Deep Space Nine and Star Trek: Voyager, which each aired for seven seasons and overlapped chronologically, and by four movies with the TNG cast.  The stardates on all of these were five digits, usually with one decimal but occasionally more.  These stardates had a general correlation with the calendar year, in which the second digit incremented between TV seasons, and the following digits increasing from xx000.0 to xx999.9 during the course of the season.

The first season of TNG began airing in 1987, and the episode named "The Neutral Zone", which aired May 18, 1988, was set on stardate 41986.0 and gave the year as 2364. Some fans, including Andrew Main and Richie Kennedy, assumed stardates roll over on January 1 every year, while others, such as TrekGuide.com, used May 25, all of them assuming 1000 stardates per year.  Subtracting the first two digits during that season (41) from the year 2364 suggests that adding the first two digits of stardates in later seasons to 2323 gives the year of that season.

As with TOS stardates, the decimal part represented the time as a fractional day, at least sometimes, and the last whole digit incremented each day, which can be observed occurring in a number of episodes.  However, there is a contradiction between the fact that they sometimes incremented by one every day, but by around one thousand every year, even though there are only 365 days in a year.

TrekGuide.com more recently declared that there are about 918 stardates per year, based on the dating in the May 1, 2001, Voyager episode "Homestead" of stardate 54868.6 to the day after the 315th anniversary of the events of the movie, Star Trek: First Contact, which took place on April 5, 2063, making that stardate be on April 6, 2378.  Andrew Main, writing before that episode aired, also suggested that there may be less than 1000 stardates in a year based upon other references, but decided that these were mistakes.

Contemporary stardates

Although stardates are used only in stories set centuries in the future, fans have used various methods to convert a contemporary calendar date into something that resembles a stardate. Several versions of the current moment are displayed above.
The official web site at StarTrek.com, Star Trek Star Fleet Technical Manual by Franz Joseph and others formerly used the calendar date in the form YYMM.DD. This had the Y2K bug, however, so 9912.31 was followed by 10001.01.  In the 1980s, reference stardates in FASA games used prefixes for each century counting forward from 2000, so the 1900s were -1/YYMM.DD, the 2000s were 0/YYMM.DD and the 2200s were 2/YYMM.DD.

The Internet game Star Trek Online is set in the year 2409, but stardates within the game progress by 1000 every year in the present, beginning in the 87000s when the game was released in February, 2010, consistent with TNG stardates projected 400 years into the future, and rolling over on or near May 25 each year.

Some, such as Andreas Schmidt and Steve Pugh, simply project stardates backwards from TNG, with stardate 0.0 occurring in 2323 and negative stardates prior to that.  This gives stardates in the current century that are six-digit negative numbers.  Pugh differs in that the three digits to the left of the decimal point increase positively from 000 to 999 during the year, even as the thousands increment negatively, so that -310999.9 is followed by -309000.0, -309000.1, etc.
Andrew Main's FAQ uses negative "issue numbers" in brackets before each sequential series of four-digit stardates, which increment by five units each day and each issue lasting about five-and-a-half years projecting backwards from TOS, with the year 2012 occurring during issue [-28] and the episodes in TOS during issue [19], after which he speculates that different methods are used.  Issue [0] in this system represents the supposed founding of the United Federation of Planets. This method has been adopted by Google Calendar.

Others, such as TrekGuide.com, devised formulas such that the current stardate would be approximately the same as what Captain Picard, Sisko or Janeway would be putting in their logs in the 24th century, as portrayed in the most recent episode, until they ended in 2001.  For instance, when one episode aired on September 28, 1987,  the stardate in the captain's log was 41153.7.  Thus, stardates in this system increment by one thousand per year, just as on TV, or on average about 2.7 per day.  The TV seasons began in September and ended between May and July, so the contemporary stardate would roll over at some point in between, and July 15, 1987, was arbitrarily chosen by some as 41000.0, although others use January 1 as the rollover date.  This seems to be the exact method used to calculate a stardate on the episode "The Adhesive Duck Deficiency" of the TV show The Big Bang Theory, when Sheldon's log gives stardate 63345.3, corresponding with the date of the Leonid meteor shower that year, November 17, 2009.

Modified Julian Dates have also been used. Star Trek 30 Years Special Collector's Edition, published in 1996 by Paramount Pictures, states on page 81:

Few Star Trek topics generate as much heated debate as the stardate system, the time calculation used by the United Federation of Planets which was introduced to the classic series by Gene Roddenberry, who borrowed the notion from the Julian date currently used by astronomers. Developed by Joseph Scaliger (who named his dating system after his father, Julius Caesar Saliger), the Julian time calculation measures the number of days elapsed since 1 Jan. 4713 BC, the date derived by Joseph Justus. In the case of the 30th anniversary of the air date for the original series (8 Sept. 1996), that's 2,450,335 days. To make it easier, astronomers only use the last five digits - making 50335 the Julian date for the Star Trek anniversary. For Star Trek, Roddenberry added a single digit after the decimal point (50335.2) to represent one of the 10 time measurements in a 24-hour period...Roddenberry borrowed the five-digit Julian date, shortening it to four digits and renaming it "stardate."
Note that the part about being named after the father is a common error; it was actually named for the Julian calendar introduced by Julius Caesar.  Also, Scaliger only counted years; it was the astronomer John Herschel who introduced counting days, and other astronomers added decimals in the 19th century. You can convert here between several types of stardates, Julian Dates and standard date/time.