He That Has Ears To Hear, Let Him Hear

Easter and the Calendar

Astronomical Applications Department of the U.S. Naval Observatory.

Gregorian Calendar

The usual statement, that Easter Day is the first Sunday after the full moon that occurs next after the vernal equinox, is not a precise statement of the actual ecclesiastical rules. The full moon involved is not the astronomical Full Moon but an ecclesiastical moon (determined from tables) that keeps, more or less, in step with the astronomical Moon.

The ecclesiastical rules are:

resulting in that Easter can never occur before March 22 or later than April 25.
(The above from http://aa.usno.navy.mil/faq/docs/easter.php)
See also - Antipas Foundation - It is an undisputable and well-known fact among Christians that the crucifixion of Christ Jesus, His death and burial, was on a Passover daytime period.  A Biblical fact documented so very well that it is neither an item for debate nor even for doubt.
The above from http://www.antipas.net/easter.htm.

See Scriptures and Easter