Why does the date for Easter change each year?

Here's an explanation, so prepare to be bamboozled, and if this leaves you confused, all I can say is "Welcome to the club! You are not alone."

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If we don't have an exact date for the birth of Christ (it wasn't December 25) and we don't have an exact date for the resurrection, what does this suggest to you? Were his followers just careless about the facts, or did these events actually take place at all? Have any of you studied the Ancient Egyptians and their religious beliefs and practices? If so, you may have noticed that there's quite a lot of similarity or parallelism between that and various aspects of modern Christianity. The names of the gods have been changed, but their family associations remain more or less the same, and the special days have fresh explanations, but there's a lot of the same liturgical pomp and circumstance and mystagogic psychobabble.

Why would that be? The easiest explanation would seem to be that at the time that Ancient Egypt and soon afterward the Roman Empire were dying on the vine, something new and fresh was needed to energize the population, but
the establishment evidently believed "If it works, don't fix it" so they didn't throw out all the old system, but simply revised it to give it a fresh look and a new lease on life, because after all, it worked for several thousands of years, so it probably could continue working for thousands more.....and it is! Since then, it's been working for 2,000 years already. And before you decide to come down on me over this, do your homework. You may learn something.