As Iranians celebrate the Persian New Year, explore the fascinating calendars still used around the world—shaped by sun, moon ...

Essentially, Easter was first celebrated by the early Christians, who followed the Hebrew calendar. Christmas was celebrated by those who lived in the Roman Empire, which followed the Julian calendar.

But why has Hanukkah only started on Christmas just five times in the ... In 1582, Pope Gregory XIII modified the then-accepted Julian calendar in order to space out the leap years to more closely ...