“Their theology and liturgy is identical. You are comparing apples with oranges.”
From this web site there seems to be major differences, not just the calendar, between the different Orthodox denominations, just as in some Protestant denominations:
http://en.allexperts.com/q/Eastern-Orthodox-1456/differences-various-Orthodox-Churches.htm
“the Greek Orthodox and Coptic Orthodox Churches r almost in full communion. there r serious attampts to acheive full communion between Oriental and Eastern Orthodox Churches.
the main reason both families r not in communion is the conflict that took place after the council of Chalcedon. there r two views about the nature of Christ; the Chalcedonian and the non-Chalcedonian.
The Chalcedonian understanding of how the divine and human relate in the person of Jesus is that the two natures (divine and human) are united in one person (Christ). This view, known as the hypostatic union, became the official theological understanding after it was endorsed by the Council of Chalcedon.
Miaphysitism (sometimes called henophysitism) is the christology of the Oriental Orthodox Churches. Miaphysitism holds that in the one person of Jesus Christ, Divinity and Humanity are united in one “nature” (”physis”), the two being united without separation, without confusion, and without alteration.
Miaphysitism has often been considered by Chalcedonian Christians to be a form of monophysitism, but the Oriental Orthodox Churches themselves reject this characterization, a position which the Eastern Orthodox and Roman Catholic Churches have begun to take more seriously.”
Oh, details, details. Quit bothering with details. ;O)
1. Since when is all experts dot com an authority on anything?
2. The coptic ‘Orthodox’ churches are not part of the Orthodox church they are part of the monophysites who split with the church over the Nicene Creed. (Usually if they are reffered to as Orthodox at all it is as the ‘Oriental Orthodox’ )
3. Many of these churches have joined up with the Roman Catholics in recent years.
The calendar is a fluke brought on uncanioncially by a Freemason Ecumenical Patriarch of Constantinople in 1921 (the Synod never approved it). It was accepted for practical and other reasons by most Orthodox Churches. The calendar is however not a theological issue. The Old Calendar is more accurate as regards Easter (in the new calendar, Easter can occur before Passover and that is incorrect; in the old one, it cannot).
Coptic Orthodox Church is not Orthodox and hasn't been part of the Orthodox Catholic Church since the 4th century (Council of Chalcedon). Their willingness to change their theology is making strides towards full communion. But they were in Christologic heresy all these centuries regardless of what they call themselves.
There is such a fluke as Orthodox Presbyterian Church. Just because someone calls it "orthodox" doesn't mean it is Orthodox. Just because the Mormons call themselves "christians" doesn't mean they are!