Module Time.Date
Dates.
of_civil (y, m, d) is day d of month m of year y in the proleptic Gregorian calendar, or None if m is not in [1;12], d is not a day of that month, or the date is out of range. Years are astronomical: year 0 is 1 BC and year -1 is 2 BC.
to_civil t is (y, m, d), the year, month and day of t. of_civil (to_civil t) is Some t.
of_days n is the date n days after 1970-01-01, or None if it is out of range.
compare t0 t1 orders dates chronologically. It is compatible with equal.