STARDATES IN STAR TREK FAQ  Part III
Last update: Feb 15 1997
Version 1.5
by Andrew Main
<zefram@fysh.org>
19960328, stardate [31]7269.00
PART III: INVESTIGATION INTO STARDATES
This FAQ addresses the problem of what stardates mean. Of course, considering
that stardates are merely a way to refer to points in time, any meaningful
answer must refer to some other standard way to refer to time. The adage
about standards is especially true here  there are so many to choose from.
Ultimately, it is desired that stardates be related to a standard currently in
use. For example, Greenwich Mean Time (GMT). This is defined as local mean
time at the Royal Observatory in Greenwich, London. Local mean time is
defined in terms of the observed noon on each day. Consequently, each day of
GMT is a slightly different length, and not even an integral number of
seconds. (Otherwise, the second varies in length from day to day, which
would be even worse.) This is, therefore, in its strictest form, not a very
good standard.
UTC (Universal Coordinated Time) is a better standard. The second is the unit
of time defined by the SI, and can be regarded as having a fixed duration.
Each day is exactly 86400 seconds, except for the occasional day of 86401
seconds used to keep in line with GMT (to within one second). To date there
have been thirty such leap seconds, the most recent on 19951231.
Theoretically there may also be days of 86399 seconds, though there have not
been any so far, and it is not anticipated that any will be needed. This is a
better standard for specifying time, but still suffers from variable day
lengths, which makes its handling awkward.
However, both GMT and UTC suffer from a more fundamental flaw: they depend on
observations made from a single planet. If the planet is changed
significantly, or is destroyed, then the time standard is meaningless.
Furthermore, anyone in a different reference frame (i.e., anyone not on Terra)
will disagree with Terrans about the order of certain events. This is a
fundamental aspect of relativity.
Fortunately, Treknology provides a solution. For FTL travel to avoid
violating causality, it has to take place in such a way that all FTL
travellers have the same frame of reference. (Refer to Jason Hinson's
"Relativity and FTL" FAQ for the explanation of all this.) The only standard
timebase that could be considered universal would be one based in this frame
of reference. It has been established numerous times in ST:TNG that there is
a Federation Timebase, which presumably is arranged in just this way.
Thus it is established that stardates are linked to the FTB. But what about
Terran calendars? Because this standard reference frame is currently unknown
to Terran science, it can be conveniently assumed to be close to the reference
frame of Terra. Because the relation to Terran time is only approximate, the
choice of GMT or UTC is irrelevant, and the distinction will be ignored from
here on.
This makes it possible to refer to points in time  unambiguously  using
the Gregorian calendar, which is what will be done for the remainder of this
FAQ. The Gregorian calendar is chosen because it is the most widely used on
Terra. Furthermore, it will be assumed that every day is exactly 86400
seconds long.
Since there must be some basis for a system, the following will be assumed, in
decreasing order of importance:
 Nothing will be arbitrary, unless it is unavoidable. The idea is that
anyone working from the same data, using the same principles, will come to the
same conclusion.
 Stardates occur in the `right' order. That is, the stardate will always
increase numerically in the direction of advancing time. From time to time it
will be necessary for the stardate to be reset to zero, but only on a finite
set of occasions. On the principle that the system be as simple as possible,
this set should be as small as possible.
 Stardates will, in general, increase at a constant rate relative to the
Federation Timebase. From time to time this rate may vary, but only on a
finite set of occasions. On the principle that the system be as simple as
possible, this set should be as small as possible.
 Stardate rates will be round numbers relative to Terran phenomena such as
days or years.
Given the above assumptions  and working by the principle that the system
should be as simple as possible  what follows is the investigation of the
stardate system. ST:TOS stardates will be discussed first; the ST:TNG
stardates can be added to the system later (and relatively easily). Note:
unless otherwise stated, all stardates specified are exact. As discussed in
the previous section, Terran times given are necessarily approximate.
The system worked out below does not attempt to explain known writing errors.
Just as Data's remark in "Encounter at Farpoint" ("Starfleet class of '78...")
is commonly ignored, errors of stardate such as those in "Dark Page" are
ignored here. Verbal bloopers are also ignored, naturally. Also, because of
their irreconcilable inconsistency, stardates other than the main one for each
episode must be ignored.
Going by the Star Trek Chronology, the first and last episodes are "The
Corbomite Maneuver" (SD 1512.2; assumed to take place 300 years after it aired
in September 2266) and "Turnabout Intruder" (SD 5928.5; early 2269).
This choice of episodes has some faults. "Turnabout Intruder" was the last
episode aired, but the stardate of "All Our Yesterdays" was later (stardate
5943.7 against 5928.5). Under the principle that stardates occur in the right
order, "All Our Yesterdays" must be taken as the endpoint for the mission.
(It makes little difference anyway, because the actual date is only
conjecture.)
Similarly, there is room for dispute over which episode comes first. "The
Corbomite Maneuver" (SD 1512.2) was first in regular production, but that
doesn't necessarily mean anything. Similarly, "The Man Trap" (SD 1513.1), the
first episode aired, is not a good starting point. "Where No Man Has Gone
Before" (SD 1312.4) was first overall in both production and stardate, but is
generally regarded as being quite distinct from the rest of the series.
"Mudd's Women" (SD 1329.1) has the earliest stardate of the episodes in
regular production, providing another possible starting point. However, the
episode "Charlie X" (SD 1533.6) contains a clear reference to Terran dates,
making all this arbitrariness unnecessary.
[Note: the Chronology lists the stardate of "The Man Trap" as 1513.1, but the
Star Trek Compendium says 1531.1. I would appreciate it if someone could
check with the episode itself, to confirm one date or the other.]
At one point in "Charlie X", Kirk states that it is Thanksgiving day on Earth.
For those not familiar with American customs, Thanksgiving day is the fourth
Thursday in November. Assuming Kirk was indeed referring to that same
Thanksgiving day (which seems likely), and accepting the Chronology's
calculation of year, this pins down the date of Kirk's statement to
22661122. Let this be the day after the initial statement of the stardate
for the episode, and the conclusion is reached that the episode started on
22661121. This is only two months different from the Chronology's
conjecture, and has the advantage of being almost completely nonarbitrary.
Stardate 1533.6 was sometime during 22661121. According to the Chronology,
the end of the series (SD 5943.7) was in early 2269. The is approximately
4400 units spanning two and a half years. A nice round number close to this
rate is 5 units per day. (4.8 units/day  0.2u/hour  is also within the
possible range. It would be less plausible, however, because it relates to
hours, which are purely a human invention, whereas days are a natural
phenomenon.)
With this rate, to make things easier, it can be assumed that any exact
multiple of 5 units is midnight. So the Thanksgiving day in question,
22661122, runs from exactly SD 1535 to just before SD 1540. Therefore, SD
5940 is 00:00 on 22690421 ("All Our Yesterdays" is on that day).
This rate puts "Where No Man Has Gone Before" in 2266, in contradiction to the
speculative date in the Chronology. (This is not a problem, because there is
no stronger evidence to back up that particular speculation.) It also set
dates for a number of other events that the Chronology has assigned
conjectural dates. It gives us a date of 22700209 for ST:TMP, which is not
acceptable. ST:TMP should occur in late 2271, to give Kirk time to have "not
logged a single star hour in two and a half years". So the stardate rate must
have changed at some stardate between 5943.7 and 7411.4.
Going by the Star Trek Chronology again, these dates may be useful. "Star
Trek: The Motion Picture" (SD 7411.4) was in late 2271, at least 30 months
after the end of the original TV series. "Star Trek III: The Search For
Spock" (SD 8210.3) was in late 2285. "Star Trek VI: The Undiscovered Country"
(SD 9521.6) was in 2293. These dates are conjectural, but they have a solid
basis. They may be moved a little without contradicting anything other than
the Chronology itself.
(By the way, ST:TMP really does have a stardate of 7411.4, despite the manuals
that say 7412.6. One of the barelyaudible messages at the Epsilon 9 station
mentions a rendezvous between two Federation ships to take place on stardate
7411.4. If you listen carefully it is also possible to make out the ships'
names and registry numbers  scout Columbia NCC621 and scout Revere NCC595.
These names and numbers match those in the list of scouts in the "Star Fleet
Technical Manual".)
TVH:STIV is about 3 months after STIII:TSFS according to Captain Kirk's log,
but this reference can be ignored because he may have meant Vulcan months.
It turns out that the stardate rate has to change sometime between ST:TMP and
STII:TWOK, as well as sometime before ST:TMP. The details of that period,
encompassing ST:TMP, can't be calculated until this bit, for the remainder of
the classic films, has been done.
The reference points to use for this are STIII:TSFS (SD 8210.3; late 2285) and
STVI:TUC (SD 9521.6; conjectured to be 2293). The gap is 1311.3 units,
covering 78 years. A suitable rate is 0.5 units per day. (0.48u/d 
0.02u/hour  is also within the possible range.)
Similarly to the first period of stardates, it can be assumed that any exact
multiple of 0.5 units is midnight. This means that the days on which
STIII:TSFS and STVI:TUC start will start at stardates 8210.0 and 9521.5
respectively. The calculation of exactly which dates these are must wait
until the details of the intermediate stardate rate have been calculated.
Neither of the periods of stardates discussed above gives a satisfactory date
for ST:TMP. It is therefore necessary to have an intermediate period of
stardates to link the two. It is possible to make this link with a single
intermediate period. This period must use up stardates much more slowly than
either of the adjacent periods.
This intermediate period can have a rate of about 0.156u/d at the most. To
have a rate any higher, this period would have to extend into ST:TOS or beyond
STII:TWOK. It would be possible to use a rate of 0.15u/d (which has the
advantage of making a standard 8hour shift exactly 0.05 units long), but this
makes the day length messy. (3u/d or 0.3u/d would be more manageable, but it
isn't possible in this case.) The most logical rate to use is 0.1u/d.
Now to place ST:TMP... It must be a fair bit more than 30 months after "All
Our Yesterdays", ideally in late 2271. To make the changeover point from
ST:TOS stardates to this period an exact midnight  it would be madness to do
otherwise  it must be a multiple of 5 units. This means that moving it one
day forward or back changes the date of ST:TMP by 49 days, because the
stardate rates differ by a factor of 50. The most reasonable date possible
for ST:TMP under this limitation is 22720110, with the changeover at SD
7340.0 (22700126). This is not quite in 2271, but close enough not to cause
problems with later dates.
And for the second changeover... It turns out that fairly sensible dates for
STIII:TSFS and STVI:TUC can be obtained by putting the second changeover at SD
7840.0 (22831005)  exactly 5000 days (500 units) after the first
changeover. This makes it all look designed. This puts STIII:TSFS at
22851014, consistent with the Chronology. It also makes STVI:TUC
22921219, which is not quite the conjectural 2293, but is close enough.
Throughout ST:TNG stardates have increased at approximately 1000 units per
year. (In fact, during ST:TNG, the second digit of the stardate indicated the
season.) From these facts, the Chronology has conjectured that ST:TNG
stardates increase at exactly 1000 units per year. Numerous references within
the series supports this conjecture. Of course, they support it because the
shows were written with that system in mind. It would be difficult to
contradict this.
However, there are a few inconsistencies in this respect within the series.
In "Eye of the Beholder" (ST:TNG, SD 47622.1; incidentally, this is the second
of (so far) three very near title clashes in Star Trek  there was an
animated Star Trek episode called "The Eye of the Beholder") an incident at
Utopia Planitia is referred to both as stardate 40987 and as eight years ago;
allowing for rounding, this gives a year length of between 704.4 and 954.4
units. In "The Pegasus" (ST:TNG, SD 47457.1), the disappearance of the
Pegasus was stardate 36764 and twelve years ago; this gives a range of 807.8
to 974.4 units per year. In "Second Sight" (ST:DS9, 47329.4), the battle of
Wolf 359 (SD approximately 44002) was exactly four years ago, giving a year
length of 832 to 834.75 units.
There are some other references consistent with an 833 unit year, but most are
not so clearly referring to Terran years. In any case, the vast majority of
references support 1000 units per year, leaving these other references as
isolated mistakes.
In "The Neutral Zone" (SD 41986.0), Data stated that the year was 2364. This
almost solves the problem of year calculations. The only problem is that Data
did not go on to say exactly what day of the year it was, so there is an
uncertainty of one year when calculating dates from this.
Note that ST:TNG stardates have five digits before the decimal point, where
ST:TOS stardates have four. This would seem to suggest a change of outlook on
the part of the Federation, from shortterm to longterm. This coincides with
the change from stardate units being convenient fractions of Terran days to
being a convenient fraction of a year. Also, the length of stardates in
ST:TOS could allow for up to about 5.4 years before needing to be reset to
zero, whereas the ST:TNG stardates only need to be reset once a century.
(Presumably one often needed to specify which period of 5.4 years one meant by
a particular stardate.)
The Chronology proceeds under the assumption that all first season stardates
were in the year 2364, and then all second season in 2365, and so on. There
isn't really any evidence to support this, but it makes things neat. The
production crew have occasionally calculated exact dates on this basis. In
order to keep things simple, it will be assumed that this is how the stardates
actually work. This makes stardate 00000.0 midnight at the beginning of
23230101.
Stardate 99999.9 should be about 50 minutes before midnight on 24221231,
after which the stardates get reset to zero again. However, it is not
possible to state this as being exact, because not all centuries are the same
length. Every fourth century contains 25 leap years; the rest have 24 each.
The difference in the lengths of individual years creates a more immediate
problem: the 1000s of units can't match up exactly with calendar years.
Obviously, one solution would be for the stardate rate to vary from year to
year, making each year 1000 units whether it is 365 or 366 days long. This is
not acceptable as a universal time system, however. The rate changing every
fourth Terran year makes things difficult for the Vulcans, and the Andorains,
and in fact almost every member of the Federation.
So the rate must make 1000 units fit a mean solar year of 365.2425 days
exactly. (Actually that's not quite exact, but that is the exact mean length
of a year by the Gregorian calendar. This is more appropriate, because the
Gregorian calendar is being used to specify dates.) 400 years is exactly
146097 days, no matter which 400 years one counts. By a happy coincidence,
this is exactly 20871 weeks. (This fact is of no practical use, except in the
construction of perpetual calendars.)
For convenience, it can be conjectured that starships on extended voyages 
and maybe some civilians too  use a standard year of length 365.2425 days.
This doesn't mean they add on an extra 5.82 hours at the end of the year, but
that they distribute it evenly throughout the year. This makes each day about
57.4 seconds longer than 24 hours. In fact, to make chronometers visually
indistinguishable from those previously in use, the second would get longer.
This standard year is exactly 31556952 SI seconds long, but is internally
divided into the usual 31536000 seconds. This makes the `chronological
second' approximately 1.00066 SI seconds, and even Data would have difficulty
distinguishing the two.
The two calendar styles could coexist quite easily, because they would rarely
be more than a few hours different. In order for them to coexist over a long
period of time, they must agree on what day of the week any particular date
falls on. (A consequence of this is that existing perpetual calendars will
still be applicable to the new calendar.) Where there would be a leap day in
the oldstyle Gregorian calendar, there is merely a jump in the day of the
week. For example, Wednesday 23960228 would be followed by Friday
23960301, missing out Thursday 23960229 which would appear in the
Gregorian calendar.
This new calendar will hereafter be called the "quadcent calendar". It comes
exactly into line with the oldstyle calendar every 400 years. Since the
origin for ST:TNG stardates is 23230101, that must be when the two calendars
match up. (The next time will be 27230101.) Hereafter, quadcent calendar
dates will be written like 2323*01*01, instead of 23230101.
SD 9521.5 corresponds to the date 22921219. The digits run out and are
reset to zero on 22950803. This starts a special `issue' of stardates,
whose sole purpose is to bridge the gap to 23230101, when the newstyle
stardates take over. In this new issue, SD 5000.0 is 23221220, almost
exactly 30 years after STVI:TUC. This makes 23230101 SD 5006.0. So
stardate 5006.0 in that issue became stardate 00000.0, and the date,
23230101, became 2323*01*01 for the purposes of stardates.
If Thanksgiving were twelve days later, these numbers would be unbelievably
neat. So neat, in fact, that one might well reach the conclusion that this
system was actually designed to work this way.
From the ST:TOS stardates we know that SD 1530 is 22661121. Extending this
back, SD 0000 is 22660119, well after the beginning of the fiveyear
mission. To go further back, we must go into an earlier issue of stardates.
In this earlier issue, SD 9995 must be 22660118 (one day before the ST:TOS
stardate 0000). This makes SD 0000 in this issue 22600729. Continuing this
process backward, it should be possible to find a sensible starting point for
all stardates.
The theory is here supported by the ST:DS9 episode "Equilibrium", which puts
Joran Bella's birthdate at stardate 0024.7, and notes that this is in 2260.
(This theory makes it 22600802.) However, the same episode puts his death
as stardate 8615.2 and 2286. This is not quite consistent with this theory,
being two years out.
None of the major reallife space events is a 0000. The 43rd issue before the
classic series has its 0000 on 20300804, and 2030 is supposed to be the year
of Zefram Cochrane's birth; this is a rather implausible candidate for the
origin. The 37th issue before the classic series has its 0000 on 20630612,
just a couple of months after Cochrane's first demonstration of warp drive
(20630405, according to ST:FC). I think the powers that be here missed a
great opportunity here. It looks like stardates just aren't based on any
significant event in space travel.
The 19th issue before the ST:TOS stardates has its SD 0000 on 21620104,
which is tantalisingly close to 2161 (Federation incorporation). Taking this
as the origin of stardates, it could mean that Starfleet originally used
oldstyle Terran dates, but found them inappropriate for deepspace use. A
few months after incorporation, then, they started up stardates.
If we call these first stardates `zerothissue', which will be written like
[0]0000, ST:TOS uses 19thissue stardates (e.g., [19]1530 is 22661121). The
partial issue to link the TCFS stardates with the ST:TNG stardates is the 20th
issue, and ST:TNG stardates are 21st issue. This notation provides a
convenient way to refer to stardates a long way from the current time.
[
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Part II 
Part III 
Part IV 
Part V 
Part VI
]
