Book of Common Prayer (page 880)

Tables and Rules for Finding the Date of Easter Day

Rules for Finding the Date of Easter Day

Easter Day is always the Sunday after the full moon that occurs on or
after the spring equinox on March 21, a date which is fixed in accordance
with an ancient ecclesiastical computation, and which does not always
correspond to the astronomical equinox. This full moon may happen on
any date between March 21 and April 18 inclusive. If the full moon
falls on a Sunday, Easter Day is the Sunday following. But Easter Day
cannot be earlier than March 22 or later than April 25.

To find the date of Easter Day in any particular year, it is necessary
to have two points of reference--the Golden Number and the Sunday Letter
for that year.

1. The Golden Number indicates the date of the full moon on or after
the spring equinox of March 21, according to a nineteen-year cycle.
These Numbers are prefixed in the Calendar to the days of the month from
March 22 to April 19 inclusive. In the present Calendar they are
applicable from A.D. 1900 to A.D. 2099, after which they will change.

2. The Sunday Letter identifies the days of the year when Sundays
occur. After every date in the Calendar a letter appears--from [A] to
[g]. Thus, if January 1 is a Sunday, the Sunday Letter for the Year is
[A], and every date in the Calendar marked by [A] is a Sunday. If
January 2 is a Sunday, then every date marked with [b] is a Sunday, and
so on through the seven letters.

In Leap Years, however, the Sunday Letter changes on the first day of
March. In such years, when [A] is the Sunday Letter, this applies only
to Sundays in January and February, and [g] is the Sunday Letter for the
rest of the year. Or if [d] is the Sunday Letter, then [c] is the
Sunday Letter on and after March 1.

To Find the Golden Number

The Golden Number of any year is calculated as follows: Take the number
of the year, add 1, and then divide the sum by 19. The remainder, if
any, is the Golden Number. If nothing remains, then 19 is the Golden
Number.

To Find the Sunday Letter

The following Table provides ready reference to the Sunday Letter of any
year between A.D. 1900 and A.D. 2099. It will be found on the line of
the hundredth year above the column that contains the remaining digits
of the year. But in Leap Years the Letter above the number marked with
an asterisk is the Sunday Letter for January and February, and the
Letter over the number not so marked is the Sunday Letter for the rest
of the year.