How Is Easter Determined?

Easter is the most important movable feast in Christianity. How is the date determined each year?

When is Easter this year?

How Is Easter Determined?

Easter falls on the first Sunday after the Full Moon date, based on mathematical calculations, that falls on or after March 21. If the Full Moon is on a Sunday, Easter is celebrated on the following Sunday.

Although Easter is liturgically related to the beginning of spring in the Northern Hemisphere (March equinox) and the Full Moon, its date is not based on the actual astronomical date of either event.

• March 21 is the Church’s date of the March equinox, regardless of the time zone, while the actual date of the equinox varies between March 19 and March 22, and the date depends on the time zone.
• The date of the Paschal Full Moon, used to determine the date of Easter, is based on mathematical approximations following a 19-year cycle called the Metonic cycle.

Both dates may coincide with the dates of the astronomical events, but in some years, they don’t.

Astronomical vs. Ecclesiastical Dates

In years in which the Church’s March equinox and Paschal Full Moon dates do not coincide with the astronomical dates of these events, there may be some confusion about the date of Easter. In 2021, for example, the March equinox in the Western Hemisphere happened on Wednesday, March 20, while the first Full Moon in spring was on Thursday, March 21 in many time zones. If the Church followed the timing of these astronomical events, Easter would have been celebrated on March 24, the Sunday after the Full Moon on March 21.

However, the Full Moon date in March specified by the Church’s lunar calendar, also called the ecclesiastical Full Moon, was March 20, 2021—one day before the ecclesiastical date of the March equinox, March 21. For that reason, the Easter date 2021 was based on the next ecclesiastical Full Moon, on April 18. This is why Easter Sunday 2021 was on April 21.

Calendar with holidays

Earliest and Latest Easter Dates

According to the Metonic cycle, the Paschal Full Moon falls on a recurring sequence of 19 dates ranging from March 21 to April 18. Since Easter happens on the Sunday following the Paschal Full Moon, it can fall on any date between March 22 and April 25. (Note: this applies only to years 1753-2400).

List of years with earliest and latest Easter dates

Holidays Related to Easter

The dates of many Christian feasts are based on the date of Easter Sunday. For example:

Why Is Easter Celebrated in Spring?

According to the Bible, Jesus Christ’s death and resurrection occurred at the time of the Jewish Passover, which was celebrated on the first Full Moon following the vernal equinox. This soon led to Christians celebrating Easter on different dates. At the end of the 2nd century, some congregations celebrated Easter on the day of the Passover, while others celebrated it on the following Sunday.

In 325 CE, the Council of Nicaea established that Easter would be held on the first Sunday after the first Full Moon occurring on or after the vernal equinox. (*) From that point forward, the Easter date depended on the ecclesiastical approximation of March 21 for the vernal equinox.

Orthodox Easter

Not all Christians observe Easter according to the Gregorian calendar; most Orthodox Christians still follow the Julian calendar.

Like the Easter date based on the Gregorian calendar, Orthodox Easter falls on a Sunday between March 22 and April 25 in the Julian calendar (years 1753-2400). In the Gregorian calendar, this corresponds to April 3 to May 10.

In some years, Orthodox Easter falls on the same day as western Easter. The next time the two Easter dates coincide will be in 2025 (April 20).

Proposed Easter Date Reforms

There have been a number of suggested reforms for the Easter date. For example, in 1997, the World Council of Churches proposed a reform of the Easter calculation to replace an equation-based method of calculating Easter with direct astronomical observation.

This would have solved the Easter date difference between churches that observe the Gregorian calendar and those that observe the Julian calendar. The reform was proposed to be implemented in 2001, but it is not yet adopted.

Another example of a proposed reform occurred in the United Kingdom, where the Easter Act 1928 was established to allow the Easter date to be fixed as the first Sunday after the second Saturday in April. However, this law was not implemented, although it remains on the UK Statute Law Database.

Topics: Dates, Calendar

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