The calculation explained by Gilf was devised so as to keep it separate from the Jewish festival of Passover or Pesach.
Pesach begins on the 15th day of the Jewish month of Nissan, and as Jewish months are determined by the New Moon, Pesach starts on the evening of a Full moon. This is almost invariably the 1st after the Veranl Equinox and so the complicated Easter calculation prevents Easter from clashing with the first day of Pesach.
The Council of Nicaea in 325 a.d. established that Easter would be celebrated on Sundays; before that Easter was celebrated on different days in different places in the same year.