Why is easter on a different date each year, and how is the date calculated?

celebrated on the Sunday following the first full moon after the vernal equinox! the vernal equinox is usually around march 21st.

Easter is on a different date each year because it's date is derived from the Jewish Passover. The bible says that Jesus's death happened around Passover so early Christians, being often Jewish, celebrated the Resurrection during Passover or on the Sunday afterwards. The Passover starts on the 14th day of the Jewish month of Nissan. Jews use a lunar calendar so each month begins with a new moon. As the moon and the Sun are not synchronised, this means the date of new moons change from year to year. After the destruction of the temple, the Jews had no central authority to decide when the new moon was so people just observed it locally. This meant passover (and hence Easter) was celebrated on different days in different places. The Christian church eventually settled on a formula - Easter would be on the first Sunday on or after the first full moon after the spring equinox, assuming the spring equinox to be March 21st (not quite right astronomically but close enough). The full moons are determined by tables as again observers in different places might differ about when the moon was actually full. Jews also came up with their own formula for determining Passover but it is different so Passover and Easter are no longer linked, though they both usually occur some time in April or late March.

I know its different. Last year it was the earliest it could be. I don't know why. answer plz! http://answers.yahoo.com/question/index;_ylt=As82PGd7_AetSBOgtUAIfTPsy6IX;_ylv=3?qid=20090324143627AAmQuVH