Every year Christians around the world look forward to the main church holiday - the Resurrection of Christ, and each time this event falls on a different day. To calculate its date, whole methods have been developed, thanks to which we know what date Easter will be, not only in 2015, but also in the coming decades.
Instructions
Step 1
The exact day of "the celebration of all celebrations," as Easter is called in the Orthodox tradition, is calculated according to the lunar calendar. The full moon closest to the vernal equinox is considered to be the starting point. The first Sunday after it will be a day of great joy.
Step 2
Since the equinox occurs on March 20 or 21, the date of Easter is between April 4 and May 8. The decision to link the celebration to the solar and lunar cycle was made in 325 at the First Ecumenical Council. Prior to this, the Resurrection of Christ was annually celebrated on Nisan 14 according to the Jewish calendar.
Step 3
On this date, the Eastern churches celebrated a feast in remembrance of Christ's suffering on the cross, which was called Easter of the Cross, and the next day - Easter of Resurrection. Naturally, the cherished date did not always fall on a Sunday, so the celebration was often celebrated on weekdays.
Step 4
In order to somehow streamline the annual cycle of services, the bishops established new rules for calculating Easter, which are based on the Julian calendar. In this way, they achieved a one-time feast for all churches.
Step 5
In 2015, we celebrate the Resurrection of Christ on April 12 in a new style. Over the past century, Easter fell on this day twice: in 1931 and 1936. This number was found according to a formula derived back in the 4th century. It takes into account many factors, including: celebration on Sunday, the date of the vernal equinox and the first full moon after it.
Step 6
A simplified version of the formula was proposed by the German mathematician K. Gauss. The main calculation is carried out using the digits of the year using the modulo operation. For the convenience of the calculation, mathematical quantities are used, indicated by the letters a and b. Each letter is calculated as follows:
a = [(19 * [2015/19] + 15) / 30] = [(19 * 1 + 15) / 30] = 4.
Here, the expression [2015/19] means the remainder of 2015 divided by 19.
So, the full moon (2015) = March 21 + a = March 21 + 4 = March 25.
b = [(2 * [2015/4] + 4 * [2015/7] + 6 * 4 + 6) / 7] = 4.
(a + b) is less than 10, which means that Easter will be calculated using the formula (22 + a + b) March Art. style. As a result, we get 22 + 4 + 4 = March 30 (Old Style) or April 12 (Old Style).
If (a + b) were more than 10, then the following formula would be used: (a + b - 9) April Art. style.
Step 7
The date for Catholic Easter is calculated differently, since Catholics use the Gregorian, not the Alexandrian Easter. Despite this, in 30% of cases, "Christ is Risen", although in different languages, still sounds simultaneously in Orthodox and Catholic churches.
