Originally posted on blog on http://HellenicGenealogyGeek.com on June 17, 2009 The last country of European Europe to adopt the Gregorian calendar was Greece in 1923 .  However, these were all civil adoptions – none of the national churches accepted it.  Instead, a Revised Julian calendar was proposed in May 1923 which dropped 13 days in 1923 and adopted a different leap year rule that resulted in no difference between the two calendars until 2800. The Orthodox churches of Greece , Bulgaria, Romania, Poland, and a few others around the Eastern Mediterranean (Constantinople, Alexandria, Antioch, and Cyprus) adopted the Revised Julian calendar, so these New calendarists will celebrate the Nativity along with the Western churches on 25 December in the Gregorian calendar until 2800. The Orthodox churches of Russia, Serbia, Jerusalem, and a few bishops in Greece did not accept the Revised Julian calendar. These Old Calendarists will continue to celebrate the Nativity on 25 December in the...