Every year, the date of Easter Sunday adjusts, unlike other Christian holidays with fixed dates. For 2017, it will fall on April 16. Why does the date change every year?
The Roman Catholic church retains the standard for setting the date. According to Christian belief, Jesus Christ was crucified during the Jewish Passover festival. Furthermore, the Bishops that comprised the Council of Nicea, which convened in 325 AD, determined that Easter should fall on the first Sunday after the first full moon that takes place after the spring equinox, given that this full moon is known as the Paschal, or Passover, Full Moon. The spring equinox itself was fixed by the church to fall on the fourteenth day of the lunar month. This identification means that the day will always fall between the dates of March 21 and April 25.
This schedule means that the other Christian holidays celebrated in conjunction with Easter Sunday, such as Good Friday, will be adjusted accordingly.
This is the calendar followed by the Western Christian Church. However, the Eastern Orthodox Church may celebrate Easter on a different date. This is because it uses the Julian calendar, while the former uses the Gregorian one. These two calendars have a difference of 13 days, which also means that the two churches celebrate Easter on separate days.
In the past, there was actually a proposal in the to fix the date of Easter on the same Sunday every year in Anglican churches. This was made by the Most Reverend Justin Welby, the Archbishop of Canterbury, who said that this could be set on the second or third Sunday of April.
Despite the differences in the identification of the date of Easter, the intent remains the same: to celebrate the resurrection of Jesus Christ after he was crucified, which also indicates that there is new life that can be found in God.