Solar calendars track the position of the sun in the sky and are used by much of the world today in the form of the Gregorian Calendar. Lunar calendars track the phases of the moon.

It didn’t work out. France switched back to the Gregorian calendar 12 years later. The Soviet Union tried its hand at a new calendar in 1929. The state shrunk the week to five days in a dual effort to ...

Due to the complexities of the various types of calendars, the date of Easter can be as early as March 22 and as late as April 25. Here's why.