Greek Calendar Change

Thursday 16th February 2023 was the 100th Anniversary when Greece finally replaced the old Julian calendar with the revised Gregorian calendar, when on that day, the date changed throughout Greece from 16th February 1923 to 1st March 1923.  The Gregorian calendar is the calendar in common use in the world today.  It is a correction of the older Julian calendar (originally proposed by Julius Ceasar) that had been in use since 1st January 45 BC.  The problem was that leap years were slightly miscalculated in the Julian calendar.  By 1582, the old calendar was 10 days behind the solar year.  The Greek calendar was changed to the Gregorian calendar in 1923, at which time the calendar was changed 13 days to bring it in line with the solar year, the last day of the Julian calendar being Wednesday 15th February. 

The main reason that Greece did not originally adopt the Gregorian calendar was that the new calendar was a Catholic idea, instigated by Pope Gregory XIII in 1582, that rectified the leap year difference.  That meant that to adopt the Gregorian calendar was to say that the Pope was right about something, which no Protestant or Orthodox Christian was willing to do at that time.   

Many Protestant countries relunctantly adopted the Gregorian calendar in the early to mid 18th century, during the Enlightenment.  However, the Orthodox world had more reason to resent any such Western introduced change, particulary by the Orthodox Church.  Even today, the adoption of the Gregorian calendar has been ignored by some Orthodox churches, while causing a schism of 'Old Calendarists' in others who refuse to adopt it, as the autonomous monastic region of Mount Athos in Northern Greece.

Most branches of the Eastern Orthodox Church continue to use the old Julian calendar for calculating the date of Easter, upon which the timing of all other moveable feasts depends.  This is why the Greek Othodox Easter differs from its Western Easter dates by one to five weeks later, only occasionally falling on the same day, the last one celebrated in 2017 and the next being in 2025.