With my usual disclaimer about being a novelist and not a historian, here's what I've discovered:
According to documents from the 3rd and 4th centuries, Christians relied on their Jewish neighbors to determine the week of the Unleavened Bread; the Sunday that fell within that week would be Easter. Following the First Council of Nicaea in 325 AD, the date of Easter was separated from the Jewish calendar and its computations for Passover.
Since then, Easter Day is always the Sunday after the full moon that occurs on or after the Northern spring equinox, which is based on an ancient ecclesiastical computation, and does not correspond to the astronomical equinox. The church defines the spring, or vernal, equinox as falling on March 21st. Easter falls on the Sunday following the first full moon after the equinox. This full moon will occur somewhere between March 21st and April 18th, inclusive. Therefore, Easter cannot be earlier than March 22nd or later than April 25th. In 2008, Easter was particularly early, falling on March 23rd. That hadn't happened since 1913, and will not happen again until 2160.Of course, there are handy tables available to find the date. But those tables are derived from something called "The Golden Number" and "The Sunday Letter". The Golden Number is computed by taking the year, dividing it by 19, and adding 1 to the remainder. For example, 2014 divided by 19 gives 106, with a remainder of 0. Adding 1 to the remainder gives a golden number of 1. Finding the Sunday Letter involves determining the first Sunday of the year, with the choices ranging from A through G. For example, if the first Sunday in January falls on the 1st, that year is an "A" year.
So...why not a fixed date? The short answer, really, is that Easter moves around from year to year in order to maintain the connection between the astronomical events (the phase of the moon and the season) which would have occurred during the Resurrection and the annual date on which we celebrate this holiday.
Whatever spring holiday or event you celebrate, I hope it's filled with family and happiness. Take some time to enjoy nature's resurrection--the new life, strengthening sun, and longer days that characterize this season. And if the Easter bunny visits (that's a whole 'nother story...blog post for next Easter maybe?), remind him to put some new reads in your basket!
