Since Jesus' death, burial, and resurrection coincided with the Jewish Passover, religious officials wanted to keep the observation of Easter around the same time as the Passover. The Jewish calendar changes every year based on solar and lunar cycles, thus changing the dates of their holidays; therefore, the date for Easter changes as well.
Perhaps you already knew this little tidbit of information; however, I did not, and I find it rather interesting. Truth is, it doesn't matter when or how you celebrate the resurrection of Jesus. If you're a believer, it only matters that you acknowledge it.