A Tale of Two Easters The formula for Easter—
Post# of 63688
The formula for Easter—"The first Sunday after the first full moon on
or after the vernal equinox"—is identical for both Western and Orthodox
Easters, but the churches base the dates on different calendars: Western
churches use the Gregorian calendar, the standard calendar for much of the
world, and Orthodox churches use the older, Julian calendar.
One rule but two calendars & two results
Gregorian Calender
the reformed Julian calendar
Julian calendar - unreformed
adopted by Julius Ceaser
When Is a Full Moon Full?
The two churches vary on the definition of the vernal equinox and the full
moon. The Eastern Church sets the date of Easter according to the actual,
astronomical full moon and the actual equinox as observed along the
meridian of Jerusalem, site of the Crucifixion and Resurrection.