Unlike holidays such as Christmas, the Epiphany, All Saints’ Day and the Immaculate Conception, the Easter is a moveable feast whose date varies from year to year, oscillating between the end of March and the beginning of April. It is a question that is asked at the beginning of each year: but when Easter falls? For 2023 the date tomorrow, April 9th, while in 2022 Easter was celebrated on Sunday 17 April. The only certainty is that Easter falls on a Sunday. But how is the date calculated and who decided it?