When did roman Catholics and greek Catholics separate?

After Christ's resurection, there was only one church (keep in mind this is still the Roman Empire), but Christianity was illegal under Roman Law. So they were secret. As Rome weekend around 300AD, the church grew in strength and the persecutions against christians stopped.

In 325 AD the Emporer Constantine allowed toleration of Christianity, but there were still quarrels amongst the several groups, such as when was the birth of Jesus, When is Easter?, Are Icons idolatory? what language etc..So Constantine gathered a representivie from each church, such as Greece, Rome, Egypt, Antioch, Judea, and Gaul (France) and ordered them to iron out their differences. This unity is known as the Council of Nicaea, and the final church became known as the HOLY ORTHODOX CATHOLIC CHURCH.

Under the rules, Easter was set, as was the birth of Christ, and icons could be allowed, each church could retain local traditions.

In 1054AD the Great Schism occurred, The Eastern Churches remained under the Ecumenical Councils and West became Catholic. After the fall of Rome, the Eastern Churches picked up the remains of the Roman Empire, and called themselves New Rome (the Byzantine Empire), as the Catholic churches fought for power, the French, English, Italian States and Spanish States were formed.

Today there cannot be another Ecumenical Council (Council of Nicaea was the first) because it requires that an Emperor be present to convene it.