Being that I am a convert, I have been trying to understand what the differences between Old Calendar Churches, and mainstream Orthodoxy. I attend a ROCOR Church, and we are on the Julian Calendar, but are there doctrinal differences as well?
It seems that if it was just an issue of the calendar, that things could be resolved quickly.
The main difference is that various groups of so-called "Greek Old Calendarists" claim that Holy Spirit abandoned "Wolrd Orthodoxy" for their abandonement of Church Calendar, in spite all of their bishops actually followed New Calendar for at least a decade, while Jerusalem, MP (now including ROCOR) and Serbia, that never abandoned Church Calendar don't claim Holy Spirite abandoned those Churches that adhered to New Calendar.
Consequently, "Greek Old Calendarists", that meanwhile formed various groups (at least three main groups, who BTW, are not in communion with each other) hold us synagogues of heretics for we either follow New Calendar (all Churches but three/four referred above), or we (the three/four referred above) are in communion with such Churches, in spite all of them did the same for at least a decade.
I'm not too optimistic about the prospects.