Calculating the date of Easter
n"Easter day, on which the rest of the movable feasts depend, is always the first Sunday after the fourteenth day of the calendar moon which (fourteenth day) falls on, or next after, the 21st of March, according to the rules laid down for the construction of the calendar; so that if the fourteenth day happen on a Sunday, Easter day is the Sunday after." 

- Webster's Revised Unabridged Dictionary (1913)