Easter can look as if it belongs to spring in the simplest possible way: wait for the season’s first full moon, then mark the following Sunday. But the calendar used by many churches follows an older and more intricate system, and that is why Easter in 2026 falls on April 5. The key phrase is not the first full moon of spring in a purely astronomical sense. It is the Paschal Full Moon, a church calendar marker tied to a fixed equinox date of March 21. In the Western Christian tradition, Easter is kept on the first Sunday after that ecclesiastical full moon, and the result is a feast that moves through late March and April rather than staying on one date each year. Under the Gregorian system, Easter can appear anywhere from March 22 to April 25, which is why the holiday is often described as a movable feast.
That movement has deep roots. The long-running calculation is known as computus, a method built to coordinate the solar year, the lunar month, and the weekly rhythm of Sunday observance. Rather than relying on live skywatching, the system uses a mathematical approximation of the moon and a fixed spring equinox. That choice made the date predictable far in advance, which mattered in periods when churches could not easily share annual announcements across regions.
The result is orderly, but it is not always identical to the sky overhead. In 2026, the Western date of Easter is Sunday, April 5. Eastern Orthodox churches, using the Julian reckoning converted to the modern civil calendar, observe Easter on April 12, 2026. That one-week gap reflects more than custom. It comes from different calendar systems and different ecclesiastical full-moon tables, even though both traditions are connecting Easter to spring, the moon, and Sunday.
The most surprising part is that the astronomical equinox and the church’s equinox are not the same thing. The ecclesiastical equinox remains fixed on March 21, even though the actual equinox often arrives on March 20 in modern centuries. That small-looking mismatch can create large differences. In some years, a full moon that appears to qualify by astronomy does not qualify in the church calculation, so Easter waits for the next eligible full moon and shifts by weeks. A study summarized from years 1500 to 2500 found that Gregorian and astronomical Easter match in most years, but not all, with 2038 standing out as one of the next notable divergences.
Older tools inside the calculation have names that sound almost medieval because they are. One of them is the Golden Number, which identifies a year’s place in the 19-year Metonic cycle, the ancient pattern used to track recurring moon phases. For 2026, the Golden Number is 13. Terms such as epacts and dominical letters also belong to this framework, showing how seriously earlier calendar makers worked to reconcile heaven’s motions with the practical need for a stable religious year. Seen this way, Easter’s changing date is less a quirk than a record of centuries of effort to make cosmic cycles, ritual memory, and communal time fit together on a human calendar.
