The Christian calendar is very dependant on the lunar cycle
Easter weekend travel chaos is nothing new but this year parents are having to cope with split school holidays as well because Easter has come so early - but why?
The date for Christmas Day never moves, so it seems baffling that Easter should.
Yet the explanation is relatively simple and surprisingly has nothing to do with religious reasoning.
Easter always comes on the Sunday after the first full moon after the first day of spring.
So as spring is arriving on Thursday and the full moon on Friday, Easter Sunday will be 23 March - the earliest since 1913.
Easter will not come this early again for approximately another 220 years.
The Christian calendar usually mirrors the Jewish calendar quite closely, but it is much more dependant on lunar cycles.
For Christians, Easter Sunday marks the resurrection of Jesus Christ.
The other Christian traditions in the lead up to Easter, like Ash Wednesday, Lent, Palm Sunday and Good Friday have all still taken place, just earlier than usual.