Just as families mark birthdays and anniversaries, so the Christian church developed its own calendar of celebration.
A Year in the Life of the Church
The pattern of the season is reflected in many religious traditions. Christians accepted this, and often adapted pagan festivals for themselves. Events in the life of Christ, and anniversaries in the life of the church, are celebrated at set times throughout the year.
Since the beginning, Easter has been the most important Christian holiday. At first, it was called the Christian Passover, to relate to Jewish Passover, and symbolized God's salvation through the sacrifice of Christ. It was a time to remember both Christ's crucifixion and His resurrection.
As early as the 2nd century, there was debate over the correct date to celebrate Easter. Some churches preferred to keep to the Jewish calendar, while others opted for a different dating system.
Initially, Easter was only a one-day festival, marking both Christ's death and resurrection. As pilgrims began to spend the festival in the Holy Land, they retraced Jesus' steps during his final week in Jerusalem, and a more complicated series of Easter services was implemented to mark the various events. By the 4th century, Palm Sunday, Maundy Thursday, Good Friday, and Easter Sunday were all celebrated by the church.
At the same time, a tradition developed where those who wanted to be baptized were prepared during the 40 days of Lent, marking Jesus' period of preparation in the wilderness.
Between AD 326 and AD 1582, Christianity determined Easter using an algorithm approved by a Church Council in AD 325, with the equinox defined as March 21. From AD 1054 (when the Orthodox and Catholic Churches split) through AD 1582 both the Catholic and Orthodox Churches celebrated Easter on the same date, still using the algorithm from AD 325. The Julian Calendar was used by the European (and Christan) communities until the Gregorian reform of 1582.
Since AD 1582 October (when the Gregorian Calendar was adopted by much of Catholic Europe), the Orthodox Easter usually falls on dates different than the Western Christian Easter, although apparently the Churches are discussing using the same formula to determine Easter - probably a formula different than that currently used by either Church.