Easter and how it is determined and why did I not ask this question before?

Easter is a moveable feast, meaning it is not fixed in relation to the civil calendar. The First Council of Nicaea (325) established the date of Easter as the first Sunday after the full moon (the Paschal Full Moon) following the northern hemisphere's vernal equinox.^[8] Ecclesiastically, the equinox is reckoned to be on 21 March (even though the equinox occurs, astronomically speaking, on 20 March in most years), and the "Full Moon" is not necessarily the astronomically correct date. The date of Easter therefore varies between 22 March and 25 April. Eastern Christianity bases its calculations on the Julian calendar whose 21 March corresponds, during the 21st century, to 3 April in the Gregorian calendar, in which the celebration of Easter therefore varies between 4 April and 8 May.