Today (easter Sunday) marks the most important festival (for want of a better word) in the Christian calendar. Indeed, you cannot be a Christian if you don't believe that Christ died on the cross and rose from the dead three days later.
Because I have always had a curious mind and asked three uncomfortable questions, I used to ask; (1) how come Easter always moves every year? (2) Why do we call it Easter? Where did this name come from? (3) Why is there always a full moon in the week just before the Easter weekend?
Well, I found answers to these questions by going back in history. It seems that the Emperor Constantine was having a lot of trouble with the Christians who by 325AD comprised something like 30 percent of the Roman Empire.
So he called all the Christian Bishops in the Empire to the town of Nicea (which is today somewhere in Turkey). This conference is known in history as the Council of Nicea. At this conference Constantine sought to align Christian events and beliefs (such as the birth and death of Christ) with pagan beliefs, traditions and holidays.. For example the Council agreed to move the date for the birth of Christ to December 25th which originally marked a pagan festival celebrating the date on which the sun starts to move North after hitting the Southernmost Tropic on December 21st.
But why do we call it 'Easter' and why does it move every year? Again, we have the pagans to thank for this. It seems that on the Friday in the week which the third full moon of the year was always celebrated by the pagans to commemorate the goddess of Spring, Oestre, (It is from her name that we get the name 'Easter'). In any case, Spring has always symbolized rebirth and reproduction (represented by eggs and rabbit). Constantine argued that it didn't matter when exactly the relevant dates were (birth and death). What was important was the fact of the actual celebration, so he got his way after a lot of argument and he converted to Christianity. Remember that in those days everybody had to have the same religion as the Emperor. So in one fell swoop Europe (the Roman Empire) became Christian.
And so, it seems that the pagan festivals have lived on although today they represent very different things.