DTI Calendar Notes


Many of the chapter and scene headings in DTI:WTC give the date in various alien calendar systems.  Where there has been prior information about alien calendars in Trek literature or screen canon, I have tried to remain consistent with it where feasible.  Since I’m a perfectionist, I constructed full calendars which I could use to select dates that were compatible with those used in prior tales.  Here are the calendars I used and some discussion of my choices behind them.

Vulcan calendar

Year of ShiKahr 9051

Vulcan Calendar

Click to enlarge

1 lik’rt (“second”) = 1.73 s
1 lirt’k (“minute”) = 54 lik’rt = 1.56 min = 94 s
1 V’hral (“hour”) = 54 lirt’k = 1.4 hr = 84.3 min
1 T’Ved (“day”) = 18 V’hral = 25.4 hr = 1.057 dy
1 T’Kuhati (“month”) = 21 T’Ved = 22.2 dy
1 R’tas (“year”) = 12 T’Kuhati = 252 T’Ved = 266.4 dy = 0.73 yr

The novels Vulcan’s Forge and Vulcan’s Heart by Josepha Sherman & Susan Shwartz contain some Vulcan date references, but I was unable to determine a coherent pattern from them.  Instead, I followed the precedent of Michael A. Martin in ENT: The Romulan War: Beneath the Raptor’s Wing.  He employed a fan-created Vulcan calendar which is explained at Marketa Zvelebil’s fan site as preserved on the Internet Archive.  The terminology and most of the length correspondences given above are from that site.

The site gives Vulcan an orbital radius of 0.56 AU around 40 Eridani A.  Using the Internet Stellar Database‘s mass estimate for 40 Eri A (approx. 0.75 of Sol’s), an orbital radius of 0.56 AU would actually give an orbital period of 177.6 days.  Oddly, their cited figure of 266.4 days is exactly 1.5 times that.  Thus, to remain consistent with Beneath the Raptor’s Wing, I had to assume that a calendar year was 1.5 orbits long.  The reasoning for that is explained in the novel, in the first scene of Chapter IV.  However, more recent estimates of 40 Eri A’s mass are more in the vicinity of 0.84  to 0.89 Solar masses.  (Thanks to “Hando” on the TrekBBS for catching this discrepancy.)  Yet the dates already established in The Romulan War seem to be based on the older estimate, so for the purposes of the fiction, perhaps we should assume that within the Trek universe, that one turned out to be right after all.

Why would a member of a binary planet pair have months, let alone 12 of them?  Perhaps the Vulcan-T’Khut orbital cycle is c. 11.1 dy (10.5 T’Ved).

ENT: Kobayashi Maru by Andy Mangels & Mike Martin gives the Year of ShiKahr 8737 = 2135, while BTRW gives the Year of ShiKahr 8764 = 2155.  BTRW also gives both exact Gregorian dates and approximate Vulcan dates in the same chapter headings.  The Vulcan dates given are not entirely consistent with the calendar from the UK site.  I chose to base my calculations on the most consistent pair of dates, near the center of BTRW:

Ch. 41-43: middle Z’at YS 8765 = Mar. 9-10, 2156
Ch. 63: middle Z’at YS 8765 = Mar 16, 2156

A Vulcan month is 3 wks, 1.2 dy long.  If middle Z’at YS 8765 = Mar 9-16, 2156, a span of 1 wk, then YS 8765 must begin c. Mar 1, 2156.  Thus,  Mar 1, 2365 would be 286.3 R’tas later.  So YS 9051 would begin 0.3 R’tas = 80 dy earlier or Dec. 11, 2364.

Alan Dean Foster’s novelization of “Yesteryear” put “the 20th day of Tasmeen” visited in the episode in the Vulcan year 8877.  By this calendar, Tasmeen 20, YS 8877 would be c. Aug. 27, 2238.  Note that the episode takes place in 2270, so this is nowhere near the “thirty Vulcan years past” stated in the episode.  32 Terran years would actually be around 44 Vulcan years.

Romulan calendar

Year 1148 After Settlement

Romulan Calendar

Click to enlarge

1 lirt’k (“second”) = 1.01 s
1 siuren (“minute”) = 50 lirt’k = 50.54 sec
1 dierha (“hour”) = 100 siuren = 84.23 min
1 eisae (“day”) = 18 dierha = 25.27 hr (25h 16m 12s) = 1.053 dy
1 khaidoa (“month”) = various
1 fvheisn (“year”) = 492.5 eisae = 518.6 dy

The Mangels/Martin ENT novel The Good That Men Do postulates that the Romulans use the Vulcan month Tasmeen and another called Havreen (probably inspired by the “Haraveen” referred to in Vulcan’s Heart).  Kobayashi Maru and BTRW give the Romulan months the same names as the Vulcan months but different durations.

The Good That Men Do:
Ch. 1: Day 5, Tasmeen = Jan. 24, 2155
Ch. 4: Day 11, Tasmeen = Jan. 30, 2155
Ch.8: Day 21, Tasmeen = Feb. 9, 2155
Ch. 51: Day 8, Havreen = on or soon after Mar. 5, 2155

Kobayashi Maru:
Ch. 4-8: Day 29-30, K’ri’Brax = July 13-14, 2155
Ch 11: Day 33, K’ri’Brax = July 17, 2155
Ch. 35: Day 39, K’ri’Brax = July 22, 2155
Epi. 2: Day 40, K’ri’Brax = July 24, 2155?

Ch. 1: Day 37, K’ri’Brax = July 22, 2155
Ch. 18: Day 3, re’T’Khutai = July 30, 2155
Ch. 25: Day 11, Khuti = Nov 8, 2155
Ch. 39: Day 10, K’ri’lior = Feb 11, 2156
Ch. 45: Day 39, K’ri’lior = Mar 11, 2156
Ch. 53: Day 42, K’ri’lior = Mar 14, 2156
Ch. 61-2: Day 43-44, K’ri’lior = Mar 15-16, 2156
Ch. 64-5: Day 2-4, et’Khior = Mar. 18-20, 2156
Ch. 74: Day 13, T’ke’Tas = May 19, 2156
Ch. 80: Day 43, T’ke’Tas = June 20, 2156

Using these dates as my references, I settled on a Romulan day length of 1.053 Earth days (1 d = 0.95 eisae), which is mostly consistent with the date intervals seen here (if you assume some chapters are earlier or later in the listed day than others).  The Romulan year must differ from the Terran year, since Feb/Mar 2155 correspond to Tasmeen/Havreen while Feb/Mar 2156 correspond to K’ri’lior.  I settled on a year length of 1.42 y = 519 dy = 492.5 eisae (assume a leap day every other year).

The term siuren for “minutes” is from Diane Duane’s Rihannsu novels.  The other unit terms were provided to me by Mike Martin, though most are clearly derived from Duane’s vocabulary (for instance, eisae is from Eisn, her name for the Romulans’ primary star).

I considered a 14-month calendar incorporating the Vulcan months, Havreen, and the month of Sharveen mentioned in Vulcan’s Heart, but the month lengths that resulted were too inconsistent, ranging from 23 to 44 eisae.  So instead I dropped Sharveen as well as the Vulcan month of T’lakht, which is not mentioned in the Mangels/Martin novels as a Romulan month, and ended up with a 12-month calendar which is consistent with the dates listed above, with only two months needing to be significantly off-pattern in length.

Per Duane’s The Romulan Way, Romulan years are measured AS (after settlement).  The Pocket Books Novel Timeline (published in Star Trek: Voyages of the Imagination) places settlement c. 750 CE.  Thus, 2155 would be c. 989 AS, and 2381 would be c. 1148 AS.  If 989 AS begins Apr 3, 2155 (in keeping with the Mangels/Martin dates), then 1148 AS begins Mar 11, 2381.

Klingon calendar

Year of Kahless 1008

Klingon Calendar

Click to enlarge

1 lup (“second”) = 1.98 sec
1 tup (“minute”) = 48 lup = 1.58 min = 95 sec
1 rep (“hour”) = 48 tup = 1.27 hr = 76.05 min
1 jaj (“day”) = 16 rep = 0.845 dy = 20.28 hr
1 Hogh (“week”) = 8 jaj = 6.76 dy
1 jar (“month”) = 6 Hogh = 40.56 dy
1 DIS (“year”) = 9 jar = 432.2 jaj = 365.32 dy

The various works of prose and comics featuring the Klingon calendar have consistently treated a Year of Kahless as being the Common Era year minus 1374, from Kobayashi Maru (2155 CE = YK 781)  to A Singular Destiny (2381 CE = YK 1007).  (Note that Year of Kahless 1 in this system, oddly enough, would be 1375 CE, c. 500 years after Kahless died.)  This is a span of 226 years, so for this to be the case, the Klingon year can differ from an Earth year by no more than 1.6 days per year.

Known Klingon month names used in Trek canon and literature include (canonical months highlighted):
Doqath, Lo’Bral , Maktag, Merruthj, nay’Poq, Soo’jen, Xan’lahr

Alexander Rozhenko was born on the 43rd day of Maktag, so it must be at least that many Klingon days long.  Miral Paris was conceived during nay’Poq, and by my estimate that would’ve been around early April 2377.  The other month names seem to have originated at a fan site that’s no longer around; it lacked a month of nay’Poq but included two additional months, A’Kahless and Jo’vos, for a total of eight months.  It also gave the month and week breakdowns and established a leap day every fifth year (hence the extra .2 jaj in the length of a DIS).  The names of the units come from Mark Okrand’s Klingon Dictionary.

Mangels & Martin gave us the following specific date equivalences:

Excelsior: Forged in Fire:
Ch. 19-36: late Doqath YK 915 = Jan 1 – 12, 2290
Ch. 40-41: early Xan’lahr YK 915 = Jan 13, 2290

The Romulan War: Beneath the Raptor’s Wing:
Prologue: late Soo’jen YK 782 = July 22, 2156


I found an 8-month year wouldn’t be feasible with these dates.  Instead I assumed 9 months, each 40.5 dy long.  The dates given in E:FIF led me to this breakdown for 23rd-century Klingon date equivalences:

A’Kahless: Apr 5 – May 14 Jo’vos: May 15 – June 24 Soo’jen: June 25 – Aug 3
Lo’Bral: Aug 4 – Sep 13 Maktag: Sep 14 – Oct 23 Merruthj: Oct 24 – Dec 2
Doqath: Dec 2 – Jan 12 Xan’lahr: Jan 13 – Feb 22 nay’Poq: Feb 23 – Apr 4

The dates may be a little earlier in the 22nd century, since 7/22 in BtRW is in late Soo’jen instead of middle.  I decided to assume that a Klingon year differed from a Terran year by much less than the maximum suggested above, a mere 0.08 dy (1.92 hr) per year.  By the 2380s, 90 years later, that would make the dates 7 days later, as shown in the above calendar.  Note that, unlike most of these calendars, these same date equivalences can be used pretty much throughout the TNG era instead of having to be recalculated for each year.

An alternative Klingon calendar can be found at http://www.housevampyr.com/main.php?title=Klingon%20Calendar&body=training/culture/calendar/calendar.html.  I was unaware of this calendar while writing DTI:WTC, so I’m not sure whether it’s consistent with the Mangels/Martin dates.

Andorian calendar

Fesoan Lor’veln Year 709 (Second year of Fesoan Orbit 178)

Andorian Calendar

Click to enlarge

Calendar shows Moons and orbit-days.  Each orbit-day is subdivided into four phases (not shown).

1 phase = 1.17 dy = 28.14 hr
1 orbit-day (od) = 4 phases = 4.69 dy = 112.56 hr
1 Moon = 4 od = 18.76 dy
1 Fesoan Lor’veln “year” = 18 Moons = 72 od = 337.68 dy = 0.92 y
1 Fesoan orbit = 4 FLY = 288 od = 1350.72 dy = 3.7 y

BTRW gave the following dates:

Ch. 27: Thirteenthmoon, Fesoan Lor’veln Yr. 463 = Nov. 18, 2155
Ch. 42: Firstmoon, FLY 464 = Mar 10, 2156

As shown onscreen in “The Aenar,” Andoria is a Jovian moon which has no natural satellites of its own.  The “Nthmoon” designations here must therefore refer to orbital cycles of sister moons orbiting the Jovian.  Between Thirteenthmoon FLY 463 and Firstmoon FLY 464 is c. 4 mo.  If there are only 13 moon cycles in the calendar, the year is 52 mo = 4.3 y.  If there are more, the year is shorter.

Star Trek Star Charts gives Andoria’s Jovian primary as Procyon VII.  This is problematical in several ways.  A Jovian that far out would have a much longer orbit; also, the gravitational influence of the white dwarf Procyon B makes it unlikely that there could be any Jovians in the system, if indeed any planets at all.

Let’s call the Jovian Fesoan (a name that originated as the Andorians’ name for their world in Shane Johnson’s The Worlds of the Federation).  I assumed three Galilean-type satellites in a 4:2:1 orbital resonance (like Ganymede, Europa, and Io around Jupiter), with Andoria in the inner position.  An orbit-day is one full orbit of Andoria around Fesoan.  A Moon is the interval between alignments of the three moons, i.e. the period of the outer moon.  Thirteenthmoon to Firstmoon is c. 113 dy.  If there are 18 Moons, each one is c. 18.8 dy, making an orbit-day 4.7 dy and the whole Fesoan Lor’veln Year 339 dy.  If these were literally “years,” Fesoan’s orbit would be too close to the star.  Instead, I took each FLY as equivalent to a season, a quarter of Fesoan’s full orbital period.  This would make that period 1356 dy = 3.713 y, giving a semimajor axis of 2.86 AU, within Procyon’s habitable zone but far enough for Andoria to be icy.  This is unlikely to be the seventh planet.  (This leaves the issue of disruption by Procyon B unresolved.)

FLY 464 (orbit 116) begins between Feb 20 – Mar 10, 2156.  At random, say Feb 29 (it’s a leap year).  FLY 708 would thus begin Sep. 30, 2380, and FLY 709 would begin Sep. 3, 2381, the date I used in the novel.

Cardassian calendar

743 Union Era

Cardassian Calendar

Click to enlarge

Final day of Waning Season omitted every third year, final two days omitted every 12th year.

1 “day” = 1.083 dy = 26 hr
1 “year” = 3 seasons = 358.58 “days” = 388.3 dy = 1.063 y

The All Our Yesterdays sourcebook put the founding of the Cardassian Union in 1591 CE, 790 years before the book.  I arbitrarily set that equal to 743 Cardassian years, giving them a length of 1.063 standard years or 388.3 dy.  Deep Space Nine seemed to me to imply that the Cardassians used the same 26-hour day as the Bajorans.  I went with a three-season calendar on the assumption that Cardassia’s climate (at least in the region where the calendar was devised) was similar to a tropical one.  Rising would be the hot, rainy growing season, Middle the cool, dry season that follows, and Waning the hot, dry season.

Deltan calendar

Year 6470 After Rebirth

Deltan Calendar

Click to enlarge

1 “day” = 1.24 dy = 29.76 hr
1 season = 51 “days” = 63.24 dy
1 “year” = 4 seasons = 204.5 “days” = 253.6 dy = 0.694 y

Lta is V2292 Ophiuchi (Hip 82588), a G8V star with a habitable zone centered around 0.74 AU.  I thus set Dhei (Delta IV)’s orbital radius = 0.742 AU.  Assuming a typical mass for a G8 star, this gives a Deltan year of 0.694 y.  The day length was chosen arbitrarily.

If 2372 is year 6470 After Rebirth and a Deltan year is 0.694 y, this means the era of Rebirth — presumably when the Deltans gave up their first space age and adopted their more introspective civilization — would have begun c. 2118 BCE.

  1. ED
    September 25, 2019 at 7:48 am

    Mr Bennett, I just wanted to pop in and compliment you on writing some very excellent STAR TREK – one picked up UNCERTAIN LOGIC in a library and that somehow turned into a very busy week or so of reading quite a bit more of your work.

    Well played, Mr Bennett, well played.

    I’m posting this here mostly because you’ve managed to define no fewer than SIX extraterrestrial calendars (and associated timekeeping elements) and one can only stand in awe of such a feat; my compliments and my Best Wishes for your future creative endeavours!

    Oh, and one more thing – how ARE Elizabeth and Mr Darcy doing? (-;

  2. ED
    September 25, 2019 at 8:08 am

    One must admit that I was particularly interested by your FLY calendar for Andoria, as I recently read AMONG THE CLANS and have been quite ‘blue’ ever since; I even went to the extent of trying to work out a rough timeline based on the length of year given in that sourcebook.

    Unsurprisingly this made me wonder what reckoning the Andorians were using before Lor’Vela persuaded them to institute their act of Damnatio Memoriae – my assumption was that Krotus the Conqueror would have instituted a calendar of his own to celebrate the New Era brought on by his achievements … and that his opponents would have reckoned their years from the DEATH of Krotus, in one of those poetic flourishes of vindictiveness which presumably contributed to the general unpleasantness prevailing during the Age of Lament.

    It also made me wonder if the Age following the reforms precipitated by Lor’Vela might be known as the ‘Age of Recollection’ or the ‘Age of Commemoration’ (as a nod to the fact it would be the only era for which OFFICIAL records would be outstanding … though one suspects that ORAL traditions of Andorian History would be preserved even where the sculpted, carved & scribed records were condemned to obliteration by edict).

    • September 25, 2019 at 8:21 am

      I’m not familiar with any of that. The novel continuity is distinct from the version in that gaming supplement, even though ENTERPRISE borrowed a few worldbuilding elements from it.

  3. ED
    September 26, 2019 at 8:04 am

    I must admit that my own approach to such niceties is shamelessly syncretic – claim that any given take of things must be true SOMEWHERE, in one timeline or the other, and shamelessly abuse that excuse to use all the bits I like and ignore all the bits that don’t.

    Hopefully Agent Lucsley won’t catch wind of this shamelessly casual attitude to continuity, otherwise he’d probably lock me up and throw away the key … after a fair trial & due process, of course. (-;

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