A festival that follows the moon: Why is Easter not on the same day every year? Here’s how the date is calculated

Easter Sunday will be celebrated this year on April 20, 2025—but unlike Christmas or Independence Day, its date changes annually. This often raises a question among many — why does Easter move every year?

The answer lies in a blend of ancient tradition and astronomical calculation that dates back more than 1,600 years. Easter is what’s known as a “moveable feast”, and its date was formally established by the First Council of Nicaea in 325 AD.

According to the rule set by the Church, Easter falls on the first Sunday after the full moon that occurs on or after March 21, which is considered the fixed date of the spring equinox in the ecclesiastical calendar.

This means Easter can fall on any Sunday between March 22 and April 25. If the full moon falls on a Saturday, Easter is the next day. If it’s on a Sunday, Easter is pushed to the following Sunday.

The lunar event used for this calculation is known as the ‘Paschal Full Moon’, a Church-derived approximation of the actual full moon based on pre-calculated tables, not astronomical observations. The reason for this lunar link is rooted in tradition: Jesus Christ’s crucifixion and resurrection took place during the time of the Jewish Passover, which itself is based on the Hebrew lunar calendar.

Interestingly, Eastern Orthodox churches often celebrate Easter on a different date, as they follow the Julian calendar rather than the Gregorian one used in the West.

In India, where Christian communities are spread across various states, the changing date of Easter influences not just religious observance but also school calendars, local holidays, and public events. Churches prepare for Holy Week, Good Friday, and Easter services based on this annual calculation.

So while the core message of resurrection and renewal remains unchanged, Easter’s date is a dynamic reminder of how faith, tradition, and celestial timing continue to shape the Christian calendar.