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.
- 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 18 inclusive. In the present Calendar they are applicable from A.D. 1900 to A.D. 2099, after which they will change.
- 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. (See Calendar below)
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. (Example: 2026+1=2027 then divide by 19=106 [106×19=2014] therefore [2027-2014=13] The Golden Number is 13 for the year 2026)
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.
To Find Easter Day
When one has both the Golden Number and the Sunday Letter for any particular year, then the date of Easter Day may be found in the Calendar, pages 21 and 22, as follows:
- The Golden Number prefixed to a day in the month of March or of April in the Calendar marks the date of the full moon in that year.
- Easter Day will be the next date bearing the Sunday Letter of that year. But when the Golden Number of a given year and the Sunday Letter of that year occur on the same date, then Easter Day is one week later.
(Example: if the Golden Number is 19-which appears in the Calendar prefixed to March 27-and the Sunday Letter is d, then Easter Day in that year will fall on March 29. If the Golden Number is 10 and the Sunday Letter is A. then Easter Day will fall on April 9. But if the Golden Number is 19 and the Sunday Letter is b, then Easter Day will be one week later, namely April 3.)
