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2.12.4. How does one calculate Easter then?




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This article is from the Calendars FAQ, by Claus Tondering claus@tondering.dk with numerous contributions by others.

2.12.4. How does one calculate Easter then?

Under the Julian calendar the method was simple. If you know the
Golden Number of the year, you can find the Paschal full moon in this
table:

   Golden                 Golden                 Golden
   Number   Full moon     Number   Full moon     Number   Full moon
   ------------------     ------------------     ------------------
     1       5 April         8     18 April        15      1 April
     2      25 March         9      7 April        16     21 March
     3      13 April        10     27 March        17      9 April
     4       2 April        11     15 April        18     29 March
     5      22 March        12      4 April        19     17 April
     6      10 April        13     24 March
     7      30 March        14     12 April

Easter Sunday is the first Sunday following the above full moon date.
If the full moon falls on a Sunday, Easter Sunday is the following
Sunday.

But under the Gregorian calendar, things became much more complicated.
One of the changes made in the Gregorian calendar reform was a
modification of the way Easter was calculated. There were two reasons
for this. First, the 19 year cycle of the phases of moon (the Metonic
cycle) was known not to be perfect. Secondly, the Metonic cycle fitted
the Gregorian calendar year worse than it fitted the Julian calendar
year.

It was therefore decided to base Easter calculations on the so-called
Epact.

 

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