Dating age difference formula
The vernal equinox is fixed to fall on 21 March (previously it varied in different areas and in some areas Easter was allowed to fall before the equinox).
The full moon is an ecclesiastical full moon determined by reference to a lunar calendar, which again varied in different areas.
In the Gregorian calendar those dates are as commonly understood.
However, in the Orthodox Churches, while those dates are the same, they are reckoned using the Julian calendar; therefore, on the Gregorian calendar as of the 21st century, those dates are 4 April and 8 May.
Easter is the most important Christian feast, and the proper date of its celebration has been the subject of controversy as early as the meeting of Anicetus and Polycarp around 154.
This is implied by Dionysius, Bishop of Alexandria, in the mid-3rd century, who stated that "at no time other than the spring equinox is it legitimate to celebrate Easter" (Eusebius, Church History 7.20); and by Anatolius of Alexandria (quoted in Eusebius, Church History 7.32) who declared it a "great mistake" to set the paschal lunar month when the sun is in the twelfth sign of the zodiac (i.e., before the equinox).
A completely distinct 84-year cycle, the Insular latercus, was used in the British Isles.
These old tables were used in Northumbria until 664, and by isolated monasteries as late as 931.
The earliest known Roman tables were devised in 222 by Hippolytus of Rome based on eight-year cycles.
Then 84-year tables were introduced in Rome by Augustalis near the end of the 3rd century.
Because of the divergence of tables mentioned above it was usual to negotiate a common date when discrepancies arose.