In 664 at Whitby Abbey it was decided to follow the teachings of Rome as to how to calculate the date of Easter. This means that Easter Sunday is the first Sunday following the full Moon after the Spring Equinox. And as the period of time it takes the Moon to orbit the Earth is roughly 29 days or one month which is in fact a modern word and comes from the old word ‘moonth’. The date of Easter Day or Easter Sunday can be as early as March 22nd and as late as April 25th.