Of all the symbols associated with Easter the egg, the symbol of fertility and new life, is the most identifiable. However the customs and traditions of using eggs have been associated with Easter for centuries.
Easter falls in the spring, the yearly time of renewal, when the earth renews itself after a long, cold winter. The word Easter comes to us from the Norsemen's Eostur, Eastar, Ostara, and Ostar, and the pagan goddess Eostre, all of which involve the season of the growing sun and new birth.
The ancient Egyptians, Persians, Phoenicians, and Hindus all believed the world began with an enormous egg, thus the egg as a symbol of new life has been around for eons. The particulars may vary, but most cultures around the world use the egg as a symbol of new life and rebirth.
With the advent of Christianity, eggs' symbolism changed from representing nature's rebirth to representing humanity's rebirth. Many Christians likened the egg to the tomb from which Christ rose, but essentially it is an adaptation of an existing pagan festival used to communicate a new message.
See the link below for a very good explanation of the dates of easter.
http://aa.usno.navy.mil/faq/docs/easter.html