Old Calendarists

Old Calendarists is the name for two groups of Eastern Orthodox churches:

• Some churches have always used the Julian calendar to determine holidays and church festivities. This means that from 1900 to about 2100, the date of a given occasion is about thirteen days later, than if the Gregorian calendar had been used.
• Some churches (and splinter groups) have switched back from the new calendar to the old one in the 20th century.

In addition, other Christian churches use the Julian Calendar:

• A few Oriental Orthodox Churches
• The Assyrian Church of the East