On Saturday, news spread that the Most Rev Justin Welby, archbishop of Canterbury, was in discussions ‘to fix the date of Easter’. This followed comments last June by Pope Francis that it was time for different churches to come to an agreement and observe a common Easter.

For Francis, talk of a common Easter meant bringing Catholic, Orthodox and Coptic Christians together to celebrate the most important festival in the Christian calendar. Apparently he joked ‘When did Christ rise from the dead? My Christ rose today, and yours next week’.

Welby, on the other hand, had something a little different in mind. He talked, not of finding a common Easter per se, but fixing it so that it always fell on the same Sunday each year – possibly the second or third Sunday of April. There has been talk of this kind of fixing for a while, notably in the Easter Act of 1928 which declared ‘Easter-day shall, in the calendar year next but one after the commencement of this Act and in all subsequent years, be the first Sunday after the second Saturday in April’. (The Act has never been made law).

It does frustrate many people that Easter moves. Is it desirable to stop it moving so much, so that it is more like Christmas?

This is potentially a more vexed issue. Because, if the purpose of the fixing is simply convenience, then those involved could be accused of not taking some the theological issues involved in the Easter date seriously.

Easter moves in part because the historical events surrounding Christ’s crucifixion and resurrection took place around Passover. Christ as the symbolic lamb is important here. There were Christians who celebrated Easter at Passover, but this was condemned at the Council of Nicaea in 325 in order to help promote clearly distinct Christian and Jewish identities. Easter had to be on the first Sunday after Passover, which was and is decided by the full moon of Nisan.

The move at Nicaea generated a problem which generated a prolonged uneasiness within debates over Easter dates: what was the relationship between the liturgical and the historical Easter? There were competing traditions – predominantly the Latin one which stated that Christ was crucified on 25 March with the resurrection on 27 March, and the Greek one which had the crucifixion on 23 March and the resurrection on 25 March. (Note: neither of these traditions, nor the present popular one placing the events at the beginning of April, have anything to do with the second or third Sunday in April…). Neither of these are readily squared with the idea that Christ was crucified at the full moon, if you accept traditional dates for the Incarnation (Christ’s birth) and his ministry. It all becomes complicated and don’t need to know the technicalities. Even Bede ultimately fudged the issue.

(For some of the technicalities, see again Immo Warntjes’s video posted last week).

The crucial bit for the modern debate is this: can anyone find a compromise which they can justify on both theological and historical grounds, as people sought to do in the Middle Ages? A justification on the grounds of bringing divided communities together could work. But a justification on the grounds that is more ‘convenient’ runs the risk of defining the central Christian festival in ways which only separate it further from the events it is supposed to commemorate, and on grounds which are nothing to do with religion.