Calendar Blog
Longer reads on calendar history and the arithmetic behind dates.
Why Britain Lost Eleven Days in 1752
In September 1752 Britain and its colonies jumped from the 2nd to the 14th. Here is why it took 170 years, and what the change left behind.
How Leap Year Rules Work Across CalendarsFrom the Julian four-year rule to the Hebrew 19-year cycle and the Islamic 30-year cycle, every calendar needs a way to absorb leftover time.
The 344-Year Road to a Global CalendarCatholic Europe switched in 1582, Turkey adopted Gregorian years in 1926. A tour of who adopted the Gregorian calendar when, and who still uses another.
How the Date of Easter Is CalculatedEaster is the first Sunday after the ecclesiastical full moon on or after 21 March. Behind that rule lies the computus, a 1700-year-old calculation.