There Easter it’s there mobile holiday par excellence: its date, in fact, it changes every year always swinging between March and April. In 2026, for example, it falls on April 5th: but have you ever wondered why?
It all depends on the first full moon of spring: Easter, in fact, it falls on the Sunday following the first full moon that occurs after March 21stthe conventional date with which it is indicated the spring equinox (although, unlike what many people think, the beginning of spring can occur between March 19th and 21st). In practice, this means that Easter Sunday can happen over a period of 35 dayswhich run from March 22nd to April 25th.
In history, however, it has not always been like this: as also reported by Treccani, the rule in force today in the Catholic Church is the one established with the Gregorian reform of the calendar, desired by Pope Gregory XIII in 1582. Previously, however, Easter was calculated following complex rules established by the Julian calendar, which used as a reference the 19-year lunar cycle and the so-called “golden number”, which assigned to each year the order number in the corresponding nineteen-year cycle.
The link between Easter and the lunar calendar depends on the fact that the Christian Easter derives from Jewish Easter (or Pesach), established to commemorate the liberation of the Jewish people from slavery and the exodus from Egypt. Originally, in fact, Christian Easter was celebrated on the Sunday following the day 14th of the month of Nisan, exactly like the Jewish one, but over the years the date became the subject of controversy since it did not always fall on a Sunday. In 325 the Council of Nicaea thus decided to separate the date of Christian Easter from the Jewish one, while continuing to calculate it based on lunar cycles.
In any case, it should be noted that even today the full moon used to calculate the date of Easter does not correspond to the real astronomical one, but to the so-called “ecclesiastical full moon”which is determined through a calculation system based onepatta – a number indicating the age of the Moon on January 1st of each year – and on Sunday letterwhich identifies which day of the week Sundays fall on in a given year. The mechanism, therefore, is built to simplify the calculation and make it predictable well in advance, without having to wait for astronomical observations.
Once the Easter date has been calculated, all the others are determined moveable feasts of the liturgical year, from Carnival to Ash Wednesday, from Ascension to Pentecost.
