Easter is the third Sunday in the paschal lunar month, or, in other words, the Sunday after the paschal lunar month's 14th day. The 14th of the paschal lunar month is designated by convention as the Paschal full moon, although the 14th of the lunar month may differ from the date of the astronomical full moon by up to two days. Since the ecclesiastical new moon falls on a date from 8 March to 5 April inclusive, the paschal full moon (the 14th of that lunar month) must fall on a date from 21 March to 18 April inclusive.