Easter date based on accurate astronomical computations


The table below shows astronomical vernal equinox and full moon dates and a 'would/could-be' Easter date derived from it, compared to the official ecclesiastical Easter dating. Please keep in mind that the astronomically determined Easter date is purely hypothetical, although in most cases it indeed is the correct Easter date. The official Easter date according to the Roman Catholic Church is not based on true (I mean accurate modern) astronomical data, but since 1583 it is determined using the Lilius/Clavius algorithm and nothing else! This algorithm was however state-of-the-art astronomy in the 16th century, when Earth was still considered to be the centre of the Universe. Before 1583 Dionysius Exiguus' method was used since AD 532, and he had extended a table from Cyrillus that started in AD 437. Before 437 it is unsure if the same rules were obeyed, and up to AD 325, when the Nicæan Council was held, it is quite sure Easter was celebrated on different dates, so for early times the 'official' date below is just a guess.

Sometimes the astronomical Easter date can and will differ from the official Easter date, such events are called Easter paradox. The astronomical Easter date is displayed in white with a red background in those cases. If the astr.PFM differs from the official one it will have a grey background, but in most cases a wrong astr.PFM does not affect the resulting Easter date. Officially, Easter should be celebrated after Luna 14 and not later than Luna 21. If the official Easter date below is on Luna 22 or later, it will have a grey background.

The algorithm used on this page is as follows:
  1. determine the true astronomical time of the vernal equinox;
  2. find the first true astronomical full moon on or after this vernal equinox;
  3. find the first Sunday after this full moon's date in Rome's timezone without Daylight Saving Time;
  4. this is assumed to be the true first Sunday after the true first full moon in spring: the Astronomical Easter Sunday.


  • The choice of Rome to set a timezone for determining the day-of-week of the astronomical Paschal Full Moon is arbitrary, one could indeed argue it should be Jerusalem (or Alexandria!); and instead of using the timezone it would be better to use the true local solar time (certainly for the more ancient years), but those corrections would not make much difference to the general behaviour of the astronomically computed Easter date - this page is merely to demonstrate the fact that differences occur between astronomical and ecclesiastical computations;
  • I will not go into details about the astronomical algorithms used, near the bottom of this page you'll find some reference sources; accurate astronomical computations are far more complex than the other Easter dating algorithms presented on this website;
  • well, some details: following modern astronomical rules, the vernal equinox is based on the heliocentric ecliptic longitude of Earth in its orbit around the Sun, not when the Sun is exactly in the equatorial plane or when day and night have exactly the same duration! and for moon phases it's something similar, especially new moon was based on first crescent visibility, but today it's its geocentric longitude with respect to the Sun!
  • this page supports Julian (before 1583) and Gregorian (since 1583) Easter dating, valid years below are from AD through . I chose AD as lowest possible year because to my opinion it is the lowest astronomically plausible year of crucifixion. Of course Easter was not celebrated until at least one year later than the crucifixion.
  • the time-of-day displayed below is in Rome's timezone including Summer Time (DST) (indicated by +1 or +2) where applicable (so this may differ from the time used for computing the astronomical Paschal Full Moon);
  • sometimes the full moon and the vernal equinox are very close to each other, e.g. 1962 (FM = VE + 05:26), 1981 (FM = VE - 01:41), 2000 (FM = VE - 02:51), 2019 (FM = VE + 03:44), where the 19 year moon cycle described on other pages of this website can be clearly seen! In fact the full moon is close to the vernal equinox more than once per 19 years, and the early Christians already had discovered an eight_plus_eleven year cycle (in fact it looks like 2 eight-year cycles that are 3 years apart). The delta between FM and VE will be bold if it is less than one day and a half;
  • Easter paradoxes of one month are likely to occur when the Full Moon is very close to the Vernal Equinox, and paradoxes of 1 week will occur if either the astronomical or the official Paschal Full Moon is before a Sunday and the other is on or after it, and sometimes astronomy puts Easter on April 26, which the ecclesiastical dating method never does;
  • when displaying the one and a half century around the Gregorian Reform, one can easily recognise the necessity of the Gregorian Caleander Reform: before 1583 there are MANY paradoxes; often Easter is 1 or 5 weeks late and the Vernal Equinox actually occurs on March 10 or 11; beginning 1583 you can actually see the effect of the calendar reform!
  • This page is not intended to let you find when Easter was actually celebrated in any year, but to show when it should be according to the Roman Catholic Church. So the Julian/Gregorian switch year is fixed to 1582, which results in 1583 having the first Gregorian Easter Date. If you want to know Julian Easter for years since 1583 you can use my calculator/rekenmachine. The main goal of this page is just to show that official ecclesiastical computation differs from modern astronomy, but still is reasonably accurate.
  • For the following columns a popup tip exists:
    • on some header fields the tip gives a bit more information (GN, Delta's, Wks., and Ep.);
    • in the 'year' column in a highlighted year the tip indicates why this year has been highlighted;
    • in the V.E. column you'll find some info about the new moon before PFM;
    • in the PFM and Easter date columns info about the moon age is given; I use a very simple approximation to estimate first moon visiblility: if the astronomical age is over hours at 18.00 Rome time w/o DST then the moon is assumed to be visible that evening;
    • at the official PFM and Easter date columns there is also some info about the Jewish Passover date, computed using the Hebrew calendar that has been in use since (probably) A.D. 359. The official Easter date will be in red or darkblue depending on how it relates to this Pesach date. A tooltip will explain it in those cases;
    • other cells MAY also have a popup tip, especially cells containing a more or less cryptic abbreviation.

Accurate astronomical Easter dating vs. Roman Catholic ecclesiastical dating

previous 19 years
First 3 moon cycles since
Nicæan Council (325-381):
  Years from Dionysius
table (532-626):
  Period around Gregorian
Reform (1501-1652):
next 19 years

Century:   Start year:   End year:   Only Golden Number:   19 year steps   only paradoxes    
Year GN Astronomical
Last Full Moon
(Rome's timezone)
Vernal Equinox
(Rome's timezone)
Paschal Full Moon
(Rome's timezone)
Ep. Official