Monday Was in Both Years
A calendar can contain an observed feast day, a legal date and a settlement convention that move differently. Calendar rules and festival records make the authority behind each date part of the datum.
calendars
4 entries
Give Us Our Eleven Days
The riot has no depositions behind it. The payment-deferral clause from the same week is still running every UK payroll. Guess which one everybody knows.
No Integer Satisfies Both
Every leap rule is a congruence system. So is every settlement calendar. Whether two of them can be jointly satisfied depends on a number nobody computes.
The Second That Ran Backwards
A unit of time is being abolished in 2035. Not because the astronomy changed, but because software could not absorb it.