Why does the date of Easter move about so much?

Very few people seem to understand how the date of Easter is calculated, or why.  I am not among that select group!  I am deeply ignorant of the details.  But I thought that I would share what I do understand, because most people don’t even know as much as I do.  And it is Good Friday, and an Easter post seems appropriate.

Easter is the anniversary of the resurrection of Jesus Christ from the dead.  The following is the sequence of events:

• Thursday night – the Jewish passover  began at dusk.  Jesus ate the “Last Supper” – which was actually the passover meal – with his disciples.  He then went out to the Mount of Olives, and was arrested.
• Friday – Jesus was tried and executed, and died before the sabbath began at dusk; in fact the Romans made sure that he was dead before the sabbath.
• Saturday – the Jewish sabbath.
• Sunday – the resurrection.

As we can see, the date of the resurrection is very closely connected with the Jewish festivals.  Because Jesus was a Jew, and was carrying out and fulfilling the Jewish law, you do want to connect your anniversary with these events.

The problem is, you can’t.  And it’s the Jews’ fault, and you can’t fix this unless the Jews change their calendar.

This is because the Jewish calendar is a lunar calendar.  It doesn’t relate to the solar calendar that we have.  It has 13 months.  So any date on that lunar calendar moves around, by about a month, when you look at it on our solar calendar.  This is why Easter keeps moving around between March and April in our (solar) calendar.

In fact the Jewish calendar doesn’t even relate that well to itself.  Because the Sabbath is on a Saturday.  But the passover moves around on days of the week.  Thus the passover does not usually start on Thursday night, immediately before the sabbath.

Now the date of passover, which is specified in Leviticus, is the 14th of the Jewish month of Nisan.  This should be on the first full moon of spring (note the lunar element to this).  The first full moon of spring is defined as being the full moon after the spring equinox.  And the spring equinox is the day on which the day and night are of the same length.

But even so the calendar doesn’t really work.  Sometimes an extra month is inserted.  I am told that, in fact, sometimes the rabbis had to adjust the calendar manually to get the passover to appear in the spring at the right point.

So the Jewish calendar is a pain to use.  On the other hand … if you don’t use it, you lose the connection with passover.

Now the decisions had to be made back in the first century AD.  At that time, the situation on calendars was not as simple as it is today.

Firstly, the Jewish calendar is a very ancient thing.  Defective as it is – as all calendars of that period were – it was used wherever the Jews had a synagogue, and so in every city in the Roman world.  It was universal.  So you could follow it anywhere in the Roman empire, or indeed outside.  Your local synagogue would provide the dates.

You could, if you wanted, use the Roman calendar instead.  You’d always know when Sunday was.  But the Roman solar calendar – the Julian calendar – was not used nearly as universally.  Cities would often use the Macedonian months, instead of the Roman ones.  The year would start and stop at different dates.  The main means of dating an event was from the election of annual magistrates.  So in your city, you might not have the choice of saying “23 March”; if, locally, nobody used March to reckon time.  In the east, indeed, nobody did use the Roman months.

The Christians of the 1st and 2nd century AD therefore faced some difficult decisions.

In this awful situation, what are the options?

You can celebrate the Sunday, on the Julian calendar, always on the same solar date.  This is simple – so long as your city uses the Julian calendar! – but then you lose all the connections with the Jewish passover.  This isn’t good, because passover is what Jesus was actually doing when he was arrested and executed.  Passover is the first holy communion.  Jesus sacrificed himself, as a perfect passover sacrifice for sin, once for all.  You want these links, because the meaning of Easter is about that sacrifice.

Or you can follow the Jewish pattern, and have the Easter celebration based on passover.  That’s simple enough; you hold it on 14 Nisan, and ask your local rabbi when that is.   But in that case, it won’t be on a Sunday.  And the resurrection did actually happen on a Sunday, the day after the Sabbath.  So you lose your anniversary.  Worse yet, your celebration date is being determined by some Jewish rabbi.  Now Christianity is illegal.  That rabbi probably hates you all.  He may even have denounced you to the authorities a few months earlier.  How can you possibly have someone like that deciding when Easter is?

So it’s really difficult.

Stepping back a little from this, the anniversary is the anniversary, not of Jesus’ death, on the passover, but of his resurrection.  If you have to choose, surely that is the more important?

Well, the ancients took a middle path between all this, and tried to hold to as much as they could.  They decided that the anniversary of the resurrection would be celebrated on the first Sunday after the date on which the passover should happen; and if the passover was on a Sunday, then Easter would be the next Sunday.

They also decided that they were just as capable of working out when the passover ought to occur as any Jewish rabbi, so they did their own calculation of this.  It wasn’t good for Christians – an illegal group – to be that much at the mercy of the hostile Jewish establishment.

Based on this, the early Christians worked out the calculation that we use today.