== The Nicene Formula ==
The computational system that was eventually worked out derives from the calendrical experiments made at Alexandria beginning in the mid-3rd century. According to this system, Pascha is first Sunday following the date of the Paschal Full Moon ("PFM") for a given year. The PFM is not, however, as commonly thought, the first full moon following the vernal equinox. Rather, the PFM is the first Ecclesiastical Full Moon ("EFM") date that falls on or after March 21 (or, what is the same thing, the first Ecclesiastical Full Moon that follows March 20). Ecclesiastical Full Moons are calendar dates that approximate
of astronomical full moons using a cycle that repeats every 19 years. March 21 is the date used for determining the PFM because it was the near the date of the vernal equinox in the late 3rd and early 4th century A.D., when the Paschal cycle was first being developed. This formula is called Nicene because some commentators in later generations attributed it to the Nicene council.
==Shortcomings of the Julian Paschalion==
== Online Paschalion Utility ==
This site allows the user to enter a year and uses Oudin's algorithm to compute the relevant dates. Although the Orthodox (Julian-based) formulas are used, the utility returns the corresponding Gregorian calendar dates. For example, in 2006 Pascha falls on Sunday, April 10, on the Julian calendar. That date corresponds to April 23 on the Gregorian calendar.