updated
Aprilis 1, 1680 AC
June 19, 72 (Fortean)
Carmie 21, 8419 (Fourth Age)
Belyuth 36, 10036 (Kryptonian)
May 12, 14 (Martian)
Sable 7, 165 (Pataphysical)
Mit 11, 8310 (Vulcan)
Anno Confusionis Calendar
As we mentioned in Mpossibilities 72:4, there was a Feb. 29th, 1900, in Orthodox Greece and Russia which had not yet changed from Old Style (Julian calendar) to New Style (Gregorian calendar). In Mpossibilities 74:4 we reported on the collector of urban legends who told of some densans who worried about their computers not being able to handle the year 2000's extra leap day. The "extra" leap day was of course Feb. 29th, not Feb. 30th, being extra only in that the last three century years weren't leap years. By the Martian calendar there was a Feb. 30th on our Jan. 28, AD 2003, followed by Feb. 31, 32, 33, ..., 56. All the "months" in the have 73 "days" .
Going back a bit, to 46 B. C., "the year of confusion", when Julius Caesar changed Quinctilis to Julius, our July, the calendar was very different, and Februarius then only had 28 days. The year began with April 1 (whence April fool's day) and which was the spring new moon. Calends was the first day of the month (new moon). Nones was 7th day of Martius, Maius, Julius or October and the 5th of other months (approximately the first-quarter moon).The Ides was 15th day of Martius, Maius Julius or October and the 13th of other months (approximately the full moon).
Thinking on such things got us "wiffing", wondering "What if ... Julius' correction calendar [actually Sosigenes'] had not been discontinued?", "What if ... we stopped trying to fight confusion and used it?", "What if ... the Fortean Mysteries SIG revived it as our own official calendar (not to be outdone by the Fortean Society or OuLiPo (Ouvroir de Litterature Potentielle) calendars with 12 28-day months and 1 29-day month, Fort and Gueules respectively or even the Golik Vulcan calendar with 12 21-t'ved t'kuhati or the Martian calendar with its 12 55- or 56-sol months or the 6 73-zetyaro loraxo Kryptonian amzet!
It is quite forteanly mysterious with 445 days and 15 months with 23, 28, 29, 31, 33 or 34 days with one within another one -- and even an unmonth (The "un-" here means not "not" but "plus one", "undecem-" meaning eleven.)!
The others started as recently as July 8, 1976 (first Mars landing),
Jan. 1, 1931 (founding year of the Fortean Society)
or Aug. 26, 1837 (birthday of Alfred Jarry)
or as unrecently as March 25, 6417 BC (beginning of Fourth Age)
or even Jan. 1, 11742 B. C. (when Erok became bethgar of Urrika, Krypton).