So next year Easter will be on . . . er

YOU MAY not have noticed, but this is a 1A year. Next year will be a 2F and last year was a 5B. But this is a 1A.

As a result, the latest school term was on the long side, the Christmas break is genuinely ages ago, retailers are complaining it's so warm the eggs are melting and families on skiing holidays are finding bald patches on the pistes.

We are talking about Easter, the greatest feast of the Christian calendar and the most conspicuously movable. It is late.

Christmas may fall without fail on 25 December, but Easter Sunday is different. Usually (but not quite always) it comes on the first Sunday after the first full moon on or after the spring equinox, which in practice means it can be anywhere between 22 March and 25 April.

In the secular, materialistic, rightsized 1990s, this is a funny way to arrange the calendar.

Calculating the proper date is no easy matter. Generations of inattentive Anglicans will have wondered at the pages in the Prayer Book entitled: "Table to Find Easter-Day" and "Another Table to Find Easter-Day".

The former contains the immortal instructions: "To find the Golden Number, or Prime, add One to the Year of our Lord, and then divide by 19; the remainder, if any, is the Golden Number; but if nothing remaineth, then 19 is the Golden Number."

Here goes: 1995 plus 1 equals 1996; 1996 divided by 19 is 105 remainder 1. Therefore the Golden Number is 1.

Now for the Sunday Letter. "To find the Dominical or Sunday Letter, according to the Calendar, until the year 2099 inclusive, add to the year of our Lord its Fourth Part, omitting Fractions, and also the number 6. Divide the Sum by 7, and if there is no remainder, then A is the Sunday Letter. But if any number remaineth, then the Letter standing against that Number in the small annexed Table, is the Sunday Letter."

Aha! 1995 plus 25 per cent (omitting fractions) equals 2493, plus 6 equals 2499, divided by 7 equals 357, remainder nothing. Thus A is the Sunday Letter.

Refer to table. Golden Number 1, Sunday Letter A: 16 April.

Of course you can cheat and turn a few pages to find a crib of all the dates of all the movable feasts (Septuagesima Sunday, Rogations Sunday etc) for the next 51 years. But even with a crib it is fantastically arcane.

The Church itself has trouble with it. The last time the sums were done, in 1982, the Church of England needed help from both the Greenwich Observatory and an unnamed person "who used a computer".

The results were explained in Synod by Canon Michael Hodge, who concluded with the remark: "In the confidence that you will have been anaesthetised by this explanation, and in the certainty that I can answer very few questions arising therefrom, I move the motion."

Why is it so complicated? The answer is that we are dealing with a great ecclesiastical collision of calendars - lunar and solar, Jewish and Christian, Julian and Gregorian - which left infinite room for confusion.

The starting point is naturally Christ's death and resurrection, which, the Gospels tell us, took place at the time of the Jewish Passover. The Jewish calendar is a lunar one: Passover begins on the night of 14 Nisan, the first month of the year, so in principle Easter should always fall then.

Alas, it is not nearly so simple. First, thanks to earliest Christian tradition the resurrection is always celebrated on a Sunday, rather than a calendar date.

Second, the Jewish calendar has a "leap month" every few years, which throws the dates around a bit. This would be fine, except that the Christian idea of how these leap months should be organised is quite different from the way Jews actually do it, which means that Passover and Easter now follow independent paths. This year they coincide; two years from now they will be 23 days apart.

Throw into the mixture all the schisms that have occurred in the Christian churches since the time of St Paul, plus the transition from the Julian to the Gregorian calendars after 1582, and you have a recipe for mayhem.

Today, the Catholic Church uses a different official method of calculation for Easter, but happily comes to the same conclusion as the Anglicans. The Eastern churches, however, do not, so the Eastern and Western Easters can be five weeks apart.

Compared to what went on in the 7th century of course, this is orderly. In 651, for example, at the court of Oswy of Northumbria, the king (following Rome) celebrated Easter on the day that his queen, Eanfleda, (following Celtic Christian practice) was marking Palm Sunday.

The secular powers have tried to sort things out, most recently in 1928 when Parliament ruled that the feast should fall every year on the Sunday following the second Saturday in April. But in the absence of assent from the Eastern churches, the Act could not be implemented. After 2,000 years, it seems, it is still too early to agree about Easter.