Astronomical And Gregorian Easter Sunday

Astronomical and Gregorian Easter Sunday

The date of Easter Sunday is commonly defined as the first Sunday that falls after the full moon, sometimes called the Easter or Paschal Full Moon, that occurs after the spring equinox. As the precise computation of the moments of the spring equinox and the astronomical full moon is complex and laborious the determination of Easter Sunday has always been based on a simplified method.

The date of the spring equinox is hereby fixed as 21 March and the ‘ecclesiastical’ full moon dates are obtained from a table based on the mean motions of the sun and the moon. The Easter Full Moon is the tabular full moon that occurs on or after 21 March and the first Sunday that occurs afterwards is Easter Sunday. The earliest possible date for Easter Sunday is thus 22 March, which can only occur when the Easter Full Moon falls on Saturday 21 March.

As the astronomical spring equinox can actually occur on 19, 20 or 21 March and the astronomical full moon can also fall a day earlier or later than its mean tabular date it sometimes happens that the Easter date, as computed from the true motions of the sun and the moon, differs from the date as determined from the ecclesiastical rules.

The following tables list the years between 1583 and 2500 when the dates of astronomical Easter Sunday and Gregorian Easter Sunday are different. The tables are based on Jean Meeus, Mathematical Astronomy Morsels (Richmond: Willmann-Bell, 1997), pp. 364–366 and Mathematical Astronomy Morsels V (Richmond: Willmann-Bell, 2009), p. 390. Also tabulated are the golden number (GN) and the Easter date difference in weeks (Δw).

From 1583 to 2000

Year	Easter Sunday				Year	Easter Sunday
	Astronomical	Gregorian	GN	Δw		Astronomical	Gregorian	GN	Δw
1590	25 March	22 April	14	+4	1825	10 April	3 April	2	–1
1598	29 March	22 March	3	–1	1829	26 April	19 April	6	–1
1609	26 April	19 April	14	–1	1845	30 March	23 March	3	–1
1622	3 April	27 March	8	–1	1876	9 April	16 April	15	+1
1629	8 April	15 April	15	+1	1900	22 April	15 April	1	–1
1666	21 March	25 April	14	+5	1903	19 April	12 April	4	–1
1685	25 March	22 April	14	+4	1923	8 April	1 April	5	–1
1693	29 March	22 March	3	–1	1924	23 March	20 April	6	+4
1700	4 April	11 April	10	+1	1927	24 April	17 April	9	–1
1724	9 April	16 April	15	+1	1943	28 March	25 April	6	+4
1744	29 March	5 April	16	+1	1954	25 April	18 April	17	–1
1778	12 April	19 April	12	+1	1962	25 March	22 April	6	+4
1798	1 April	8 April	13	+1	1967	2 April	26 March	11	–1
1802	25 April	18 April	17	–1	1974	7 April	14 April	18	+1
1818	29 March	22 March	14	–1	1981	26 April	19 April	6	–1

From 2001 to 2500

Year	Easter Sunday				Year	Easter Sunday
	Astronomical	Gregorian	GN	Δw		Astronomical	Gregorian	GN	Δw
2019	24 March	21 April	6	+4	2296	22 March	19 April	17	+4
2038	28 March	25 April	6	+4	2299	23 April	16 April	1	–1
2045	2 April	9 April	13	+1	2316	9 April	16 April	18	+1
2049	25 April	18 April	17	–1	2336	29 March	5 April	19	+1
2057	25 March	22 April	6	+4	2339	2 April	26 March	3	–1
2069	7 April	14 April	18	+1	2353	26 April	22 March	17	–5
2076	22 March	19 April	6	+4	2372	23 April	26 March	17	–4
2089	27 March	3 April	9	+1	2390	1 April	8 April	16	+1
2095	27 March	24 April	6	+4	2394	24 April	17 April	1	–1
2096	8 April	15 April	7	+1	2410	28 March	25 April	17	+4
2106	25 April	18 April	17	–1	2417	9 April	2 April	5	–1
2114	25 March	22 April	6	+4	2421	25 April	18 April	9	–1
2119	2 April	26 March	11	–1	2429	25 March	22 April	17	+4
2133	22 March	19 April	6	+4	2437	29 March	22 March	6	–1
2147	23 April	16 April	1	–1	2448	22 March	19 April	17	+4
2150	19 April	12 April	4	–1	2451	23 April	16 April	1	–1
2170	8 April	1 April	5	–1	2467	27 March	24 April	17	+4
2171	24 March	21 April	6	+4	2468	8 April	15 April	18	+1
2174	24 April	17 April	9	–1	2471	12 April	5 April	2	–1
2190	28 March	25 April	6	+4	2486	24 March	21 April	17	+4
2201	26 April	19 April	17	–1	2488	28 March	4 April	19	+1
2221	8 April	15 April	18	+1	2491	1 April	25 March	3	–1
2245	20 April	13 April	4	–1	2492	20 April	13 April	4	–1
2277	25 March	22 April	17	+4	2495	17 April	10 April	7	–1

According to the traditional Easter reckoning, both Dionysian and Gregorian, the extreme possible dates for Easter Sunday are 22 March and 25 April.

In the astronomical reckoning, however, Easter Sunday can occur as early as 21 March (as in 1666) and as late as 26 April (as in 1609, 1829, 1981, 2201 and 2353). Even 20 March is a possible date in the astronomical reckoning, when the spring equinox falls on 19 March and the full moon later on the same date (being a Saturday). However, in the period considered here (1583–2500), this never happens.