Why does the date on which Easter falls change every year?

Because the Pop tells us when to celebrate and we have to listen to him most of the time, and not all of the time.

Why should you care?  Normally, Easter lands in April, however, there's been a few times it landed in March.

On julian calander Christian say Jesus Christ was crucified on March 25  we follow easter to be associated with passover which is a lunar holiday  first sunday after a full moon after spring equinox 

Up until the time of the Council of Nicea in 325 AD, the anniversary of the Savior’s resurrection was celebrated on various dates in the spring of the year. The Emperor Constantine, in an attempt to unify the various opposing factions of his empire, particularly the Christians and Pagans, unified their holidays. He did this by recognizing the dates of the pagan holidays and imposing on them Christian names and practices.

The ancient Saxons celebrated the return of spring with an uproarious festival commemorating their goddess of offspring and of springtime, Easter. Since this pagan holiday occurred at about the same time as the Christian observance of the resurrection, those two feast days were united. Although the Christian practice of the holiday was to commemorate the resurrection of the Savior, the name, Easter, was retained. The name was eventually changed to its modern spelling, Easter. However, the dates that determined the pagan holiday that was its predecessor remained in force.

Therefore, Easter falls on the first Sunday after the full moon that happens on or next after the March equinox (March 21). The extreme dates for Easter are March 22 (in the years 1818 and 2285) and April 25 (in the years 1886, 1943, 2038). 5,700,000 years are required for cyclical recurrence of Gregorian Calendar Easter dates. The most common of the 5700000 dates is April 19.

It may be of interest to note that both the Easter bunny and Easter eggs are hold-overs from early pagan practices. The symbol of the Easter bunny originated with the pagan festival of Easter. The goddess, Easter, was worshiped by the Anglo-Saxons through her earthly symbol, the rabbit.

The egg has been a symbol of rebirth in most cultures from the earliest times.. Eggs were often wrapped in gold leaf or, if you were a peasant, colored brightly by boiling them with the leaves or petals of certain flowers. The exchange of eggs in the springtime is a custom that was centuries old when Easter was first celebrated by Christians.

Because the first full moon after the spring equinox always falls on a different date on the Roman calendar. 21 March-23 April.

The death and resurrection of Jesus Christ took place at Passover.  This is a Jewish festival set by their lunar calendar.  Unfortunately, over the past 1,986 years, the Jewish authorities have changed the basis of their calendar a number of times.  Both Western and Eastern Christians came up with a formula that made Easter coincide with Passover in the original Jewish calendar - but they disagree, usually by a week (although the Eastern Easter can be very late).

In the Western Church, Easter is the first Sunday after the first full moon after the spring Equinox - although it's not the actual Equinox, but a nominal one!  The Anglo Saxon calendar had a month called Eostre which was the 30 days starting with the spring Equinox - the actual Equinox, not a nominal one!  Since the celebration always fell within that month, it is called Easter in the English speaking world.  Most other languages call it the equivalent of Passover.  This year, the Jewish Passover and the Christian feast coincide, but that doesn't happen very often.

Cuz its meant to be on a Sunday, and it eont always fall on the same date.

Because it is based on the moon - the Sunday after the Friday which follows the first Full Moon after the Vernal Equinox.  This changes every year.

It's based on the Lunar calendar - go figure!

The date of Easter changes, because the Paschal full moon can fall on various days in different time zones. But because Easter falls on a Sunday after the March 21 spring equinox, it will always occur on a Sunday between March 22 and April 25.