It's basically the slavic orthodox countries that use the old calendar, plus certain groups that have more or less broken out of other churches. The monasteries

It's basically the slavic orthodox countries that use the old calendar, plus certain groups that have more or less broken out of other churches. The monasteries on Athos also use the old calendar, even the monasteries that belong to new calendarist jurisdictions. A fun fact is that visas to Athos, which is a semi-autonomous island in Greece where only men are allowed (not even female animals!) and that prince Charles loves, are issued in the Julian calendar. It's worth noting that even most new calendarists, like the Greeks, still celebrate Easter at a different date than the Catholics. The calendar question is extremely infected and especially the Russians consider it a very crucial issue. https://en.wikipedia.org/wiki/Mount_Athos https://en.wikipedia.org/wiki/Mount_Athos