By Jonathan Badger
FrenchRevCal-Ruby is a script that converts standard Gregorian dates
into those used by the French Revolutionary Calendar (also known as
the French Republican Calendar; see
http://en.wikipedia.org/wiki/French_Republican_Calendar). This was the
calendar used by the Republican government in France between 1793 and
1805. Its structure reflects the secular, rational ideals of the time,
with 12 months of a uniform 30 days, broken into 3 10-day “weeks”. The
remaining five days of the year (or 6 in leap years) were filled with
monthless year-end celebrations. Year 1 of the calendar started in
September 1792, with the official founding of the French
Republic. Each day of the year was associated with a plant, animal, or
tool, replacing the saints of Catholic tradition.
The script “revcal” without any arguments returns the current date in
the revolutionary calendar, along with the associated concept for the
day. Providing a date (in a standard format that the Ruby Date class
can parse), returns the value for that date instead (which is useful
for looking up one’s birthday, for instance.)
I use the arithmetic of the Date class to calculate the number of days
since September 22, 1792 (Day 1 of Year 1). Then it is a simple matter
of jumping forward by the number of days in each year until the number
of remaining days is less than a length of a year. Then dividing this
number by 30 gives the month, and the modulo the day. The only real
issue is what counts as a leap year. There are several conflicting
ideas as to the method of computing the revolutionary leap years. I
have gone with the method (which apparently Emacs also uses), of
treating the historical leap years as 3, 7, 11, 15, and 20, and to
treat subsequent years divisible by 4 that aren’t divisible by 100
(unless they are also divisible by 400), as per the Gregorian method.
I have compared my results to Emacs, as well as confirming the correct
conversion of famous dates such as 18 Brumaire 8 (Nov 27, 1799; the
date of Napoleon Bonaparte’s coup against the French Directory,
effectively killing the revolution as an ideological movement),
None!
(The MIT License)
Copyright © 218 (that is, 2010 in the reactionary Gregorian system)
by Citizen Jonathan Badger
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