Easter is different every year because it is a movable feast determined by a combination of the solar and lunar calendars. Specifically, Easter is celebrated on the first Sunday after the first full moon occurring on or after the fixed date of March 21, which is the ecclesiastical approximation of the vernal (spring) equinox. This full moon is called the Paschal full moon. Since the timing of the full moon varies each year, the date of Easter shifts between March 22 and April 25. This method was established by the First Council of Nicaea in 325 AD to unify the celebration date among Christians.
In addition, historical calendar reforms, such as the switch from the Julian to the Gregorian calendar, also influence the calculation, and some Christian groups (like Orthodox churches) use the older Julian calendar, which leads to different Easter dates in some years.
Thus, Easter does not have a fixed date like Christmas; it is tied to lunar cycles around the spring equinox, making its date vary every year.
