Why Easter was later this year (2019)
In 2018 Easter Sunday fell on 1st April, but this year it fell three weeks later 21st April, this is because its date is based on a Lunar calendar cycle. The moon takes approximately 28 days to orbit the earth, we see this as the moon changes from a new moon, waxing through the next two weeks into a full moon and then waning another two weeks back to a new moon.
In ancient times in the middle east, the moon was a very visible and an easily used method to measure weeks and months. Many religions and their cultures use the moon rather than the sun – the Lunar calendar is used by Hindus, Moslems, Jews and Chinese – each month starting on the New Moon (when the first sliver of moon becomes visible against the dark of the moon). Indeed, the latest Chinese New Year (year of the Pig) happened on the New Moon that fell on 5th February, Ramadan will start with the New Moon on 5th May and the next Jewish New Year (Rosh Hashannah) will be on the New Moon on the evening of 29th September.
But we all know that the solar year runs for 365¼ days a year and to keep in track with the orbit of earth around the sun we merely add one day every four years. The problem with a Lunar calendar is that there are more than 12 Lunar months in a solar year; a 12-month lunar year is about eleven days shorter than the solar year. So, what the Jewish religion does – in which many Jewish festivals are based on nature’s annual cycle – is to have 7 Leap Years within every 19 Years where an extra month is added for a leap year. By doing this over time the two calendars (Solar and Lunar) keep in synchronisation. This year (5779) is one of the seven Leap Years, so an extra month (four weeks) has been added in.
Back to Easter – the Gospels of Matthew, Mark, and Luke say that Jesus was crucified after The Last Supper and many believe this was in fact the Seder meal, which Jews celebrate annually at the beginning of the Passover which is on the Full Moon (15th) of that month. This also ties in with Passover being celebrated on the first Full Moon following the vernal equinox; therefore, Easter Sunday is the first Sunday after the beginning of the Passover and the Full Moon.
John Kerbel, Croydon Synagogue