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Last update: Feb 15 1997 Version 1.5
by Andrew Main <zefram@fysh.org>
1996-03-28, stardate [-31]7269.00



Before the Federation was founded, everyone involved in space travel used their own time system. Terrans used the Gregorian calendar and UTC; Vulcans used their own calendar. Initially the Federation used the Terran calendar, just as it used the Terran language and had its headquarters on Earth. This system proved to be extremely unpopular, especially with the Vulcans, who liked a calendar to have some logic about it. (Alternating 30-day months with 31 is fine, but sticking a 28 in the middle of that lot is just silly.)

Starfleet bureaucrats quickly devised a compromise system -- which didn't match anyone's calendar. Midnight on 2162-01-04 (only a few months after the incorporation of the Federation) was arbitrarily declared to be stardate zero, and stardates increased at the arbitrary rate of five units per Terran day. This recognised the importance of Terra to the Federation, but also allowed anyone to convert stardates to their own calendar by simple mathematical formulae.

The system having been cobbled together in a rush, the numbers became unmanageable fairly soon. What would have been stardate 10000 (midnight on 2167-06-27) was made stardate 0000 again. The first group of stardates could be referred to, when necessary, as zeroth-issue stardates, such as [0]1234, and the new issue as first-issue stardates, such as [1]1234. This reset to zero continued to occur every five and a half years, until 2266, when the 19th issue of stardates started. The Federation now having survived a little over a century, referral to stardates several issues ago was becoming increasingly common. That year, Starfleet put together a committee to investigate what type of stardate system would be more acceptable.

The committee's report, in 2267, recommended that the stardate rate be slowed to 0.1 units per day. This would make the same number of digits as had been previously used, and had covered five and a half years, cover two and a half centuries. It was decided that this system should be field-tested between stardates [19]7340 and [19]7840 -- 500 units, 5000 days. So from 2270-01-26 to 2283-10-05 this system was used. It proved to be unpopular, because one always had to specify an extra digit after the decimal point in order to get the sort of precision one had had with the older stardates. Terrans who had grown accustomed to the five-per-day rate found it difficult to adjust.

As a result, it was decided in 2280 that at the end of the test period (SD [19]7840) the new rate should not continue. Instead, a 0.5 units per day rate would be used, which would solve the main problems of both earlier systems. Four digits (before the decimal point) would last more than fifty years; it would rarely be necessary to use extra digits; and the five-per-day rate would be preserved. (Five of a different digit, but still five.) This system was used from stardate [19]7840, and was intended to be a permanent change.

With the length of starships' missions continually increasing, it started to look rather comic for starships to keep in time with the daily cycle of a planet they would sometimes have no contact with for years at a time. Keeping to its yearly cycle still had some logic, but keeping to a 24-hour day as well -- which necessitated the use of leap days -- was just silly. In 2318, over 150 years after the incorporation of the Federation, it was decided that starships should start to use a rationalised calendar, which would keep the years the right length but make the day slightly longer.

In keeping with this longer-term view of time, the stardates would be increased to five digits, and the rate changed to match this new rationalised year. A rate of 1000 units per mean year would be convenient. This would make it impossible to instantly work out the time of day from the stardate, but Terrans tend to prefer the traditional hours, minutes and seconds for specifying times anyway.

What would have been stardate [20]5006.0 -- midnight on 2323-01-01 -- became stardate [21]00000. At the same time, all Earth ships switched to the new-style calendar, and the stardate rate was changed to match it. This system has remained in use up to the present (SD [21]51000, 2374*01*01).


Here's when the classic movies are set:

Star Trek: The Motion Picture           7411.4  2272-01-10
Star Trek II: The Wrath of Kahn         8130.3  2285-05-07
Star Trek III: The Search For Spock     8210.3  2285-10-14
The Voyage Home: Star Trek IV           8390    2286-10-09
Star Trek V: The Final Frontier         8454.1  2287-02-14
Star Trek VI: The Undiscovered Country  9521.6  2292-12-19

Helpfully, STV:TFF occurs in 2287, as the Chronology conjectures. These dates make Vulcan months about four times as long as Terran ones. Kirk's birthday (STII:TWOK) is the 7th of May. (The 22nd of March, conjectured in the Chronology, is taken from William Shatner's birthday.) "The Deadly Years" (SD 3478.2) was 2267-12-15, and Kirk was 34 then, which means that his birthdate must be 2233-05-07. The year is consistent with the Chronology.

In ST:TNG, date calculations are much easier, because of the 1000 units per year rate and the quad-cent calendar. The year can be obtained from the first two digits, and the day from the rest -- there is no need to consider leap years. Here are a few significant dates:

Enterprise-D commissioned              40759.5  2363*10*05
Encounter at Farpoint                  41153.7  2364*02*26
Datalore                               41242.4  2364*03*30
Skin of Evil                           41601.3  2364*08*08
Future Imperfect                       44286.5  2367*04*15
Emissary (ST:DS9)                      46379.1  2369*05*19
Descent, Part II                       47025.4  2370*01*10
Parallels                              47391.2  2370*05*23
Caretaker (ST:VOY)                     48315.6  2371*04*26
Star Trek: Generations                 48632.4  2371*08*19
Enterprise-D destroyed                 48650.1  2371*08*26
The Way of the Warrior (ST:DS9)        49011.4  2372*01*05
Enterprise-E launched                  49027.5  2372*01*11
Star Trek: First Contact               50893.5  2373*11*23

The commissioning date of the Enterprise bears a suspicious resemblance to the launch date of Sputnik I (1957-10-04). This is designed; in fact the Enterprise date was supposed to be 2363*10*04, but a mistake was made. There is a trap when calculating these dates that would make any stardate appear to represent a date one day earlier than it should. It would appear that Sternbach and Okuda fell right in it.

The "Future Imperfect" date is Riker's birthday; his 32nd according to the Chronology (the Chronology lists a birth year of 2335, but no date). "Parallels" is Worf's birthday. Using the "Datalore" and "Descent, Part II" stardates, Lore's lifespan can be calculated at 5 years, 286 days.

The Organian peace treaty between the UFP and the Klingon Empire lasted from SD [19]3198.4 ("Errand of Mercy", ST:TOS) to [21]49011.4 ("The Way of the Warrior", ST:DS9). This is a little over 104 years, from October 2267 to January 2372.

There is a slight problem with some of the ST:TNG first season stardates. "The Battle" (SD 41723.9), "The Big Goodbye" (SD 41997.7), "Angel One" (SD 41636.9) and "The Arsenal of Freedom" (SD 41798.2) all have stardates after "Skin of Evil" (SD 41601.3), but show Tasha Yar alive. It seems that the production crew learnt from this, because they have kept stardates in order ever since. To make these stardates make sense, we must assume them to be slips of the captain's tongue. (More obvious verbal errors were made in "The Deadly Years", "Datalore" and "Birthright, Part II".)

Data stated in ST:FC that he had not used his "multiple techniques" for "8 years, 7 months, 16 days, 4 minutes, 22 [seconds]". That would be a date of approximately 2365*04*07, or a stardate of approximately 42263.4. This is early second season, between episodes, well after Yar's death and well before "In Theory" -- an as-yet unrevealed lover.


It has been calculated that stardates begin on 2162-01-04. It is quite possible, of course, to continue stardates back in time from that point, using negative issue numbers. Within each issue the stardates will still increase in the direction of advancing time; only the issue numbers will be unusual.

To start with, midnight on 2162-01-04 is stardate [0]0000. This means that midnight on 2162-01-03 can be referred to as stardate [-1]9995. SD [-1]0000, consequently, was 2156-07-14. The fact that stardates were not actually in official use at that time is irrelevant.

It seems possible that negative-issue stardates are used in the 23rd century to refer to events prior to 2162. When going as far back as the 20th century, though, the old-style Gregorian calendar has always been used by the crew of the Enterprise. In fact, they have never been canonically observed to use stardates to refer to any time earlier than 2260. Of particular interest is the final log entry in ST:FC: "Captain's log, April 5th, 2063...", indicating that in official contexts stardates are not used for dates that early, or at least are not universally used.

It is possible to continue stardates back to the 20th century, but the issue numbers get sufficiently large (in the negative direction) to be awkward. This table shows the issue origins for the next few years:

[-36]0000  1964-11-18       [-24]0000  2030-08-04       [-12]0000  2096-04-19
[-35]0000  1970-05-11       [-23]0000  2036-01-25       [-11]0000  2101-10-11
[-34]0000  1975-11-01       [-22]0000  2041-07-17       [-10]0000  2107-04-03
[-33]0000  1981-04-23       [-21]0000  2047-01-07        [-9]0000  2112-09-23
[-32]0000  1986-10-14       [-20]0000  2052-06-29        [-8]0000  2118-03-16
[-31]0000  1992-04-05       [-19]0000  2057-12-20        [-7]0000  2123-09-06
[-30]0000  1997-09-26       [-18]0000  2063-06-12        [-6]0000  2129-02-26
[-29]0000  2003-03-19       [-17]0000  2068-12-02        [-5]0000  2134-08-19
[-28]0000  2008-09-08       [-16]0000  2074-05-25        [-4]0000  2140-02-09
[-27]0000  2014-03-01       [-15]0000  2079-11-15        [-3]0000  2145-08-01
[-26]0000  2019-08-22       [-14]0000  2085-05-07        [-2]0000  2151-01-22
[-25]0000  2025-02-11       [-13]0000  2090-10-28        [-1]0000  2156-07-14

Looking at today's date, 1994-05-23 is SD [-31]3890. Right now, 12:43pm UTC, is SD [-31]3892.64. The first episode of Star Trek aired on stardate [-36]3300.31.

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