According to the Orthodox religion, today is Palm Sunday. Easter is probably the biggest celebration in the Orthodox calendar and they follow the ancient timelines, which they would argue is right...
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.
Easter this year is actually next week then!