COG Ahnsahnghong ] The Passover was disappeared at the Council of Nacaea.

A] The Eastern Church and the Western Church.

The Council of Nicaea was an international council of religious leaders from the Eastern and Western Churches, held at Nicaea in Asia Minor in 325 A.D. under the leadership of the Roman Emperor Constantine. The major issues on the agenda, discussed during with Arianism that denied the Trinity. Especially, the matter of determining the date of the Passover Communion had been disputed since the mid-second century, and it was brought to an end when the Passover was completely abolished at the Council of Nicaea.

The Passover controversy started after all the apostles died and the Early Church was divided into the Eastern Church and the Western Church. The Eastern Church, which was governed by the patriarch of Constantinople in Asia Minor, and the Western Church, which was ruled by the Pope from Rome, celebrated the Passover to commemorate the death of Christ on different dates from each other.

The Eastern Church held the Passover Communion on the 14th day of the first month in the sacred calendar and celebrated the Day of Resurrection on the first Sunday after the Feast of Unleavened Bread (the 15th day of the first month in the sacred calendar), according to the teachings of the Bible. On the other hand, the Western Church did not celebrate the Passover, and instead held Communion at Easter.
Why did the Eastern and Western Churches celebrate the Eucharist on different dates?
It was because the Western Chruch changed the date of the Lord's Supper at its own discretion, emphasazing the resurrection of Jesus. This difference in date caused much confusion among the Christians traveling from east to west. When they traveled to Rome after celebrating the Passover and the Feast of Unleavened Bread, they became confused and surprised to see the Eastern Church holding Communion at Easter.