PROGRESS TOWARDS THE reunification of the Western and Eastern Apostolic Churches is moving quickly. While there are many doctrinal differences which need to be harmonized, there is one obvious point which ought to be considered early on.
This year, Easter — the Feast of the Resurrection of Our Lord — was observed on the same date in both the Catholic and the Eastern Orthodox calendars, and in 2011 it will be likewise. However, the rules for calculating the date of Easter by the Churches are different, and so there is often variation.
An obvious sign of unity would be that Christians around the world celebrate this greatest feast on the same day, despite other calendar differences.
In general principle, Easter is the first Sunday after the first Full Moon after the Vernal Equinox; and as the mystery of the Passion and Resurrection of Christ ties in typologically, historically, and is a fulfillment of the Jewish festivals, Easter ought to be the Sunday following the start of Passover, which itself is based in principle on the same astronomical cycles.
After the destruction of Jerusalem by the Romans, there was no general agreement among the scattered Jewish authorities regarding the calculating of the date of Passover, and there was some variation on the day of its celebration. So the First Council of Nicea decreed that Christians should all celebrate Easter on the same day, and that the calculation of the date of Easter would be done independently of Jewish authorities.
Following the Council, various calculations of the date of Easter were proposed, and while they all attempted to calculate the date based on the principles given above, they are at best estimates, and so vary a bit, and so disunity in observance continues to our day. While the ancients had remarkably precise astronomical information, they did not have particularly good calculation tools, especially regarding fractional numbers, and so the formulae they used in calculations had to be simple.
Church authorities have stated that the unity of the observance of Easter is more important than precise mathematical calculations; for example, it would likely be schismatic if one ecclesial community would independently use a new, more precise calculation of Easter when the main Churches retained their existing system. All the Churches of Apostolic origin ought to use the same calculations by general agreement and so celebrate on the same day.
There is strong sign value by observing Easter on the Sunday following the start of Passover, but it would not be fitting for the people of the New Covenant to defer to the authorities of the people of the Old. But our evangelical work is strengthened by ensuring that we and the Jews both observe the slaughter of the Paschal Lamb, both in its type and fulfillment, at the same time. However, Orthodox Jewish authorities are dedicated to keeping their calendar synchronized with the seasons and Moon, for they too are concerned with fitting sign value. Jew and Christian alike ought both defer to a Higher Authority rather than personal preference: this helps resolve the dilemma.
In my opinion, fixing the calculation for Easter would be the easiest step towards the unity of practice among the Churches. As this date has a strong objective component, arguments about the relevant facts ought to be minimal.