Julian Calendar

In 46 B.C., Julius Caesar ordered the conversion of the reformed Roman lunar calendar to a solar calendar. The ninety-day intercalation fixed a developing mismatch between the seasons and the months in which they had historically fallen. 

  • The Roman municipal year had become approximately three months “ahead” of the seasons prior to this intercalation, thus spring started in June. 
  • To make the correction, the year 46 B.C. was given 445 days and was dubbed ultimus annus confusionis, or "the final year of the confused counting." 
  • The new calendar, which was based on the Egyptian solar calendar, had a 365-day year with an extra day in February every fourth year. 
  • The Julian year has an average length of 365.25 days after adding this leap year and day, which is quite near to the real solar cycle. 

The Julian calendar (O.S., or Old Style) has been in use in the West for over 1,600 years, and it is still the foundation for the “Old Calendarist” Orthodox Christian liturgical calendar, which is utilized by all Orthodox Christian churches to establish Easter dates.

You may also want to learn more about Global Calendar Systems here.