This article has been modified. The original is archived here.
As much fun as I was having with the calendar I designed in Star Dates and Calendars, the system is a tad too unworkable. Yes, I can write a computer program to generate dates, but it is no fun to try to calculate those dates in Excel. (And odds are, whoever would be using this system in this world would have designed it for even simpler applications.)
Absolute time is kept in an adapted form of Julian Days.
As the standards board was meeting in the late 19th century, This blog entry was made on 20220312, which would be star date 2459651.
If you have a handy Tcl interpreter, you can calculate star dates with the clock command:
clock format [clock scan $date] format %J
In Excel, you can use the built in date functions. Excel uses a serial date system. Day 1 is the January 1, 1900. To convert between Sublight stardates and Excel serial dates, Subtract 2415018.5. (Julian dates are noon to noon.)
Humans are lazy, and will end up shortening that. This committee met in the late 19th century, and so the nearest rollover date in the past would be Julian Day 2400000 (Tue Nov 16, 1858). The next rollover day in the future will be 2500000 (Sun Aug 31, 2132). So it's standard practice to simply ditch the leading digits unless you are addressing dates well in the past, well into the future, or you happen to live in the years surrounding a rollover. And hope you aren't like the people in my second book who are on a ship that leaves Earth in 2490000 (21050415) and won't get where they are going until 2510000 (21600117).
While absolute dates are great for calculators, it's not very useful to people. No attempt is made to make metric years and months line up with Gregorian calendar years or months. They are just a way to break up absolute time into useful, userfriendly chunks.
To convert a stardate into an Excel serial date: DATE=(STARDATE2415018.5)
A day is 24 hours long. A year is 364 days. The year is broken into 13 months of 28 days each. (13 * 28 = 364)
The names of the months are based on the Zodiac:
Number  Month  Starts 

1  Aries  1 
2  Taurus  29 
3  Gemini  57 
4  Cancer  85 
5  Leo  113 
6  Virgo  141 
7  Libra  169 
8  Scorpio  197 
9  Ophiuchus  225 
10  Sagittarius  253 
11  Capricorn  281 
12  Aquarius  309 
13  Pisces  337 
To calculate your Metric year:
int(floor(STARDATE/364))
This blog was posted in metric year: 6757
To calculate your Metric day of the year:
int(floor(STARDATE)) % 364
This blog was posted on the day of the year: 103
To calculate your Metric month:
(int(floor(STARDATE/28)) % 13)+1
This blog was posted on the month of : 4 (Cancer)
or
int(floor(DAY_OF_YEAR/28))+1
This blog was posted on the month of : 4 (Cancer)
To calculate the day of the month:
(int(floor(STARDATE)) % 28)+1}
This blog was posted on the day of: 20
or
(DAY_OR_YEAR % 28)+1
This blog was posted on the day of: 20
The days of the week are the traditional days, and the do line up with the days of the week back on Earth.
1  Sunday  
2  Monday  
3  Tuesday  
4  Wednesday  
5  Thursday  
6  Friday  
7  Saturday 
To calculate your Day of the week:
(int(STARDATE+1) % 7)+1
This blog was posted on a: 7 (Saturday)
proc FORMAT_DATE {STARDATE} { set YEAR 364 set MONTH 28 set MONTH_LIST { {} Aries Taurus Gemini Cancer Leo Virgo Libra Scorpio Ophiuchus Sagittarius Capricorn Aquarius Pisces } set DAYS_OF_WEEK {{} Sunday Monday Tuesday Wednesday Thursday Friday Saturday} set year [expr {int(floor($STARDATE/$YEAR))}] set monthidx [expr {(int(floor($STARDATE/$MONTH)) % 13)+1}] set month [lindex $MONTH_LIST $monthidx] set dayweek [expr {(int($STARDATE+1) % 7)+1}] set dayofweek [lindex $DAYS_OF_WEEK $dayweek] set dom [expr {(int(floor($STARDATE)) % $MONTH)+1}] return "$dayofweek, $month $dom, $year" }
1930000  9997 B.C.  Saturday, Capricorn 13, 5303  Oldest settlements in Damascus 
918025  Thu Jun 01, 2200 B.C.E.  Thursday, Aries 18, 2522  Umm al Binni Crater formed 
954550  Wed Jun 01, 2100 B.C.E.  Wednesday, Virgo 3, 2622  Epic of Gilgamesh Written 
347724  Sun Jan 07, 3761 B.C.E.  Sunday, Cancer 21, 955  Start of the Hebrew Calendar 
1721424  Sat Jan 01, 0001 C.E.  Saturday, Gemini 13, 4729  Start of the Common Era (aka A.D.) 
1720321  Tue Dec 25, 0004 B.C.E.  Tuesday, Gemini 2, 4726  Birth of Christ (Estimated) 
2101070  Sun Jun 01, 1040 C.E.  Sunday, Gemini 7, 5772  Movable Type invented (China) 
2400000  Tue Nov 16, 1858 C.E.  Tuesday, Virgo 9, 6593  Start of current epoch 
2415386  Tue Jan 01, 1901 C.E.  Tuesday, Ophiuchus 23, 6635  Turn of the 20th Century 
2440423  Sun Jul 20, 1969 C.E.  Sunday, Virgo 28, 6704  Apollo 11 Touched down on the moon 
2451911  Mon Jan 01, 2001 C.E.  Monday, Aries 8, 6736  Turn of the 21st Century 
2460034  Thu Mar 30, 2023 C.E.  Thursday, Leo 11, 6758  Page last Cached 
2500000  Sun Aug 31, 2132 C.E.  Sunday, Taurus 21, 6868  Start of next epoch 
2536727  Fri Mar 22, 2233 C.E.  Friday, Aries 12, 6969  Birth of James T. Kirk 
NOTE: All of the calculations for metric time use the full star date (2459317 VS 59317). You will get very different answers because 2400000 is not divisible by 364. Aries was chosen as the first month to line the calendar up with the zero axis of the plane of the ecliptic. Which was placed there because Aries also happens to be the sign of the Vernal equinox, which is where certain traditions in the Mediterranean/Near East started the astronomical/astrological year.
Because every month is the same length, and every day of the year happens on the same day of the week, generating a calendar is very, very easy:
















