Itâ€™s Easter once again. A time when believers get to celebrate the death, crucifixion and resurrection of Jesus Christ.
However, have you ever wondered why, unlike other Christian holidays say Christmas which is celebrated on 25 December, Easter dates change every year, hence the name 'movable feast.'
If you havenâ€™t realized, the Easter holiday usually falls anytime between 22 March and April 25. This year, Easter Sunday will take place on 21 April.
How Easter is determined
The lent season (period of 40 days which comes before Easter in the Christian calendar), is usually based on the Lunar calendar, unlike other holidays which are based on the Gregorian Calendar.
The lunar calendar is based on the moon phases while the Gregorian Calendar is based on the sun phases.
Usually, Easter falls on the first Sunday after the first Paschal moon either on or soon after the vernal equinox, which is the first equinox of the year. Once the full moon date is set, then itâ€™s easy to determine when Easter will be.
Â Why do the dates change every year?
Easter dates are determined by the Pascal full moon which can fall on various days in different time zones.
According to the Bible, the death and resurrection of Jesus Christ took place during the Jewish Passover. This was celebrated on the first Pascal moon on or soon after the vernal equinox.
According to an article on ThoughtCo, in 1583 there was a table which was recorded by astronomers to determine all the future Ecclesiastical full moons.
Ecclesiastical rules are that the Easter Sunday date falls on the first Sunday after the first full moon following the vernal equinox which is fixed at 21 March. This means that Easter can never take place before the 22 March or any date after 25 April.
If we take into account the vernal equinox date, which fell on 20 March this year, and the full moon which is set to happen on the 19 April, then Easter Sunday was calculated to take place on Sunday 21 April.
In 2018, the Easter Sunday date fell on April 1, this year it will take place on April 21 and in 2020, the Easter Sunday will fall on April 12.
Will Easter Sunday date be fixed?
In 2016, the Archbishop of Canterbury suggested having the Easter dates fixed soon. This will however not be possible in the next four years since, according to Telegraph, the calendars have already been printed out.
Pope Francis also said that he is open to the idea of having the Easter Sunday date fixed to avoid confusion.