What determines Easter to fall on the date that it does?

Hello.

" Easter falls on a different day each year. How is the day for Easter determined?
The day for Easter will fall on the first Sunday after the first full
moon after the Vernal equinox (remember that?). The day of the the
Vernal equinox is March 21st."
source: University of Rhode Island - Trivia
http://www.uri.edu/ce/faceit/astronomy/TA's/TQ2A10.htm

"The date on which Easter falls varies from year to year, but Easter
Sunday is always the first Sunday after the first full moon following
the vernal equinox - for the western church. The vernal equinox
signals the beginning of Spring (in the Northern hemisphere)."
source: Australian Government - Culture & Recreation
http://www.cultureandrecreation.gov.au/articles/easter/

"Easter is a religious holiday that is celebrated in the springtime.
In the Western Church, which roughly consists of Protestants,
Catholics, and Anglicans, Easter falls on the first Sunday following
the first full moon that appears on or after the spring equinox (March
21).
 According to this timeline, Easter always falls between March 22 and
April 25. The Orthodox Eastern Church also regards Easter as a
"movable" holiday, but it does not necessarily coincide with the
celebration of the West. Although Easter can fall on the same day in
the East and West, the Eastern Church generally observes the holiday a
week or more after the West. "
source: Birthday Express
http://www.birthdayexpress.com/bexpress/planning/Easter.asp

Also see: A Tale of Two Easters, which discusses how certain Eastern
Orthodox churches' tradition of using the Julian Calendar has affected
their observance of Easter.
http://www.factmonster.com/spot/easter1.html

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search strategy:
"easter falls" "full moon" vernal
easter  "first full moon" "march 21

I hope this helps.

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Clarification of Answer by juggler-ga on 06 Jan 2005 21:05 PST

I notice that the University of Rhode Island URL didn't parse
correctly. Try this instead:
http://tinyurl.com/6n37a

The New Testament mentions nothing about celebrating an "Easter
Festival". The sanctity of special times meant nothing to the early
Christians. Easter, as we know it today is a continuation of pagan
spring festivals, with the easter bunny representing fecundity. Also
the easter egg is similarly representative. The term "Easter" is not a
Christian name. It is equivalent with Astarte/ Beltis/Ishtar, whose
name is found on Assyrian [ pagan] monuments]
So the question remains, should Christians celebrate a time named
after a pagan god?.
Jesus gave the answer when he instructed his disciples to remember his
death and to keep remembering it.Luke 22;19.." Keep doing this in
remembrance of me".
First Corinthians 11;26.."As often as you eat this loaf and drink this
cup, you keep proclaiming the death of the Lord, until He arrives".
This is properly done each year on Nisan 14, in the Jewish calendar.
In 2005, this date equates with March 24th.
In contrast, Jesus said absolutely nothing about celebrating his birthday.

Surprised no one mentioned that the English Easter name and festival
both derive from Eostre / Eastre (from Bede) goddess of spring and
dawn (also the likely progenitor of oestrous, oestrogen). Her festival
was kept at the vernal equinox. As such, in keeping with almost all
Christian festivals, symbols, liturgy, and writings, Easter was
embraced or hijacked.

Best