Why Does the Date of Easter Change Every Year?

The date of Easter changes every year because it is not tied to a fixed calendar date. Instead, it is determined using a method that combines the solar year, the lunar cycle, and early Christian tradition. This approach was established to reflect the historical timing of the resurrection of Jesus Christ while maintaining consistency across the Christian world.

Easter is connected to the Jewish Passover, which follows a lunar calendar. According to the New Testament, the crucifixion and resurrection of Jesus took place during the Passover period. Because Passover is based on the cycles of the moon rather than the solar year, its date changes annually. Early Christians initially celebrated Easter around the same time as Passover, but this led to variations in observance across different regions.

To resolve this, Church leaders met at the First Council of Nicaea in AD 325. There, a standard method was agreed upon. Easter would be celebrated on the first Sunday after the first full moon following the spring equinox. For calculation purposes, the equinox was fixed on March 21, even though the actual astronomical equinox can occur on March 20 or 21.

Using this system, the process for determining Easter is straightforward. March 21 is used as the reference point. The first full moon that occurs after this date is identified. The following Sunday is then designated as Easter Sunday. Because both the full moon and the calendar weekdays shift each year, Easter does not fall on the same date annually.

So, let us be specific and walk through an example of how the date of Easter Sunday is calculated. We begin with March 21, which is fixed as the reference date for the spring equinox. If the first full moon after March 21 falls on April 3, then we look for the next Sunday that follows this full moon. If that Sunday is April 7, then April 7 is celebrated as Easter Sunday. This method explains why Easter can change each year while still following a consistent and predictable rule.

As a result, Easter can occur on any Sunday between March 22 and April 25. This wide range explains why Easter sometimes arrives early in the spring and other times much later. The variation is not random but follows a predictable pattern based on well-established rules.

The changing date of Easter highlights the historical effort to preserve unity among Christians while remaining faithful to the events surrounding the resurrection. It reflects a calendar shaped by history, observation, and careful calculation. Understanding this process helps explain why Easter moves each year and why it continues to be linked to both the rhythms of nature and the foundational events of Christianity.