According to Zeller's Congruence, the day of 29 Feb, 1600 is Tuesday. However, the cal command shows it as Friday.Is there a bug in cal's code or a limit on the range of years which Zeller's congruence can predict the day for.
The calendar produced is that for England and her colonies.
Try September 1752.
So dates before this time may not fall on the weekdays one might expect from extrapolating a modern calendar.
If you're using
gcal, you can give it the
--gregorian-reform option to set the date and duration of the discontinuity.