Among the many great Christian Orthodox holidays, Easter is paramount. Celebrations of the triumph of the blessed Christ Resurrection are passing, that is, there is no specific fixed date for Easter in the Orthodox calendar. This is due to the connection of New Testament history with the Old Testament.
The feast of the blessed Resurrection of Jesus Christ in the Orthodox calendar can fall on one of the Sundays of the period from April 4 to May 8. This is due to the gospel story that on the eve of the resurrection of Jesus Christ, Jews celebrated their Passover, which is a remembrance of the Jewish exodus from Egypt, as well as the preservation of life of the Jewish first-born during the last Egyptian execution committed by God to instruct the ungodly pharaoh.
The New Testament scripture tells us that the resurrection of Christ came next Sunday after the Sabbath of Jewish Passover. For the Orthodox Church, it was important to maintain the historical sequence of celebrated events. Jewish Passover must pass first, and only then Christ's Resurrection comes.
Jewish Passover time depends on the solar-lunar calendar. According to the Jewish lunar calendar, the Old Testament Passover was celebrated on the 14th of the month of Nisan (Aviva). During the establishment of the Julian calendar in the Roman Empire, this event became transient - it fell on the first full moon after the vernal equinox (that is, after March 21, according to the old style). Thus, in order not to violate the sequence of the gospel narrative that Christ was resurrected after the Passover, the fathers of the First Ecumenical Council (325) decided to celebrate Christian Easter the next Sunday after the full moon. If we take into account the fact that Jewish Easter could fall from April 21 to April 18 according to the old style (at this time the first full moon after the spring equinox may fall), then the New Testament Easter Sunday, respectively, falls on the interval from 22- March go to April 25 according to the old style (new style - April 4 - May 8).
If the full moon fell on the day of April 18 on Sunday (that is, Jews celebrated their Easter at that time), then the Christian celebration was carried forward a week in advance (on April 25 of the old style and, accordingly, on May 8 of the new calendar).
Currently, there is the so-called Orthodox Easter for several decades to come. This is a calendar that indicates the time of the celebration of Orthodox Easter after the Jewish holiday. So, in 2014 Easter was on April 20th, and in the coming 2015, the main triumph of Orthodoxy will be celebrated on April 12th.
