what have you learned recently?

[Skaperen]

i could add that the Gregorian calendar (not perfect) repeats every 400 years with exactly 20871 weeks (coincidence?), so for usage over the Gregorian calendar, that would be 20871/4800 or about 4.348125 weeks per month. i don't have the scientific figures for the moon and earth but 365.2422 is familiar, though i tend to use 365.2425 for calendar purposes.