In 325CE the Council of Nicaea established that Easter would be held on the first Sunday after the first full moon occurring on or after the vernal equinox. From that point forward, the Easter date depended on the ecclesiastical approximation of March 21 for the vernal equinox.
The earliest possible date for Easter is March 22, The last time it occurred was 1818 and the next time will be 2285.
The latest possible date for it is April 25. The last time it occurred was 1943 and the next time will be 2038.
By the way-the next time Easter will fall on March 27 will be in 2157.