Originally Easter celebrated on the second day of Passover, so it could be any day of the week.
In the year 325, Emperor Constantine's. (Constantine) of the Roman Empire and the assembly of the Night Sierra (The Council of Nicaea) decided that Easter should be on Sunday. This is the day that Jesus Christ was resurrected. Easter, this falls on a Sunday so. The first Sunday After the full moon in the Spring Equinox, which could be any day between March 22 -25 April.
During this same Christians have traditionally celebrate the start-up monster first. That is the custom of the candles Passover (Paschal Candle) The flame that is reminiscent of the resurrection of Jesus. Is like a light that shines out of darkness.