Sunday, April 13, 2025
It was nearly Easter Sunday today.
Easter, as you may know, is the first Sunday after the full moon after the spring equinox.
This year the spring equinox was at 9.01am on 20th March.
The first full moon after that was this morning at 1.22am.
If the full moon occurs on a Sunday we have to jump to the next one.
So Easter is next Sunday.
But only just.
And it was even closer than that.
1.22am BST is 12.22am GMT, i.e. just 22 minutes into Sunday.
If the full moon had been half an hour earlier it would have been on Saturday.
And Easter would have been today.
But the full moon really was at 1.22am.
The date of Easter is based on Rome, not Greenwich.
There was no Greenwich meridian in 325AD when the First Council of Nicaea set the rules for determining the date of Easter.
And 12.22am GMT is 1.22am CET.
So Easter is next Sunday.
But in fact the date of Easter has nothing to do with the actual spring equinox.
That's because the First Council of Nicaea decreed that the spring equinox was always on 21st March, even when it wasn't.
This year's it's 20th March but the church's Easter rules assume it's 21st March instead.
This year it makes no difference whatsoever to the date of Easter.
But in 2019 it made four weeks difference.
The actual equinox was Wednesday 20th March and the next full moon was Thursday 21st March, which would have made Easter Sunday 24th March.
But the church's rules said the equinox was Thursday 21st March so the next full moon was Thursday 18th April so Easter was Sunday 21st April.
The same thing will happen in 2038 when Easter will be kicked ahead from 28th March to 25th April, the latest possible date.
But in fact the date of Easter has nothing to do with the actual full moon.
That's because the First Council of Nicaea also simplified the dates of full moons to avoid astronomical complications.
They noted that the dates of full moons repeat, near enough, every 19 years.
So they knocked up a 19 year cycle of full moon dates and used that instead.
It's quite a complicated cycle involving epacts, golden numbers and leap years so let's not get into that here.
But there's always one ecclesiastical full moon in the period 21st March to 18th April inclusive.
And Easter is always the Sunday after that, somewhere between 22nd March and 25th April.
Table to find the date of
the Easter Full Moon |
Golden
Number |
Years |
Full Moon |
| I | 1976 1995 2014 2033 | April 14 |
| II | 1977 1996 2015 2034 | April 3 |
| III | 1978 1997 2016 2035 | March 23 |
| IV | 1979 1998 2017 2036 | April 11 |
| V | 1980 1999 2018 2037 | March 31 |
| VI | 1981 2000 2019 2038 | April 18 |
| VII | 1982 2001 2020 2039 | April 8 |
| VIII | 1983 2002 2021 2040 | March 28 |
| IX | 1984 2003 2022 2041 | April 16 |
| X | 1985 2004 2023 2042 | April 5 |
| XI | 1986 2005 2024 2043 | March 25 |
| XII | 1987 2006 2025 2044 | April 13 |
| XIII | 1988 2007 2026 2045 | April 2 |
| XIV | 1989 2008 2027 2046 | March 22 |
| XV | 1990 2009 2028 2047 | April 10 |
| XVI | 1991 2010 2029 2048 | March 30 |
| XVII | 1992 2011 2030 2049 | April 17 |
| XVIII | 1993 2012 2031 2050 | April 7 |
| XIX | 1994 2013 2032 2051 | March 27 |
We're in the 12th year of the 19 year cycle this year.
The table gives the date of the ecclesiastical full moon as April 13th.
So Easter is the Sunday after that, i.e. next Sunday, April 20th.
But fundamentally the date of Easter is based on new moons rather than full moons.
The ecclesiastical calendar is divided into lunar months each of which starts with a new moon.
The important thing Easterwise is the date of the first ecclesiastical new moon on or after 8th March.
An ecclesiastical full moon is then deemed to occur thirteen days after this new moon.
And Easter is the first Sunday after that.
Again there's a 19 year cycle, and again 2025 is year 12 in that cycle.
The ecclesiastical tables give the dates of the new moons in year 12 as follows.
1st Jan, 31st Jan, 1st Mar, 31st Mar, 29th Apr, 29th May, 27th Jun, 27th Jul, 25th Aug, 24th Sep, 23th Oct, 22nd Nov
31st March is the first new moon after 8th March.
The full moon is then deemed to be 13 days later.
And Easter is the first Sunday after that.
31st March wasn't really the date of the new moon, that was 29th March, the day of the partial solar eclipse.
But 13 days after 31st March is 13th April, i.e. today, and that really is the date of the actual full moon.
It's all a bit rough and ready but generally speaking it works.
Another way of looking at it is to consider the "paschal month", i.e. the lunar month with Easter in it.
The paschal month always starts with a new moon on or after 8th March.
And Easter is always the third Sunday of that paschal month, always without fail.
In summary...
Unofficially speaking, Easter is the first Sunday after the full moon after the spring equinox.
This year that's 20th April, the Sunday after the actual full moon on 13th April.
Officially speaking, Easter is the first Sunday after the ecclesiastical full moon after the ecclesiastical equinox.
This year that's 20th April, the Sunday after the imaginary full moon on 13th April.
It doesn't always match up like that.
But most years it does, including this year.
So it wasn't nearly Easter Sunday today, sorry.
But a few tiny tweaks to the rules and it could have been.
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