Resurrection of Christ, hand painted icon. Resurrection of Christ - Easter, is the biggest holiday for all Christians, called "the holiday of all holidays". It is believed that the Resurrection of Jesus Christ is the greatest event in the history of the human race. Easter is among the so-called movable holidays and is determined depending on the first spring full moon. According to the Orthodox tradition, the Resurrection of Christ is preceded by Great Lent. It begins seven weeks before Easter and includes 40 days and Holy Week. It was approved in memory of the 40-day fast of Jesus Christ and the last week of the Savior's earthly life. During this time, Christians should repent, purify their souls and bodies and thus prepare for the worthy reception of the holiday. In the Gospel texts, it is often mentioned that Jesus Christ during his life repeatedly predicted his crucifixion and resurrection. The events associated with Christ's Resurrection take place in the days surrounding the Jewish holiday of Passover, so from the beginning the celebration of Easter has been associated with the Jewish Passover. Because of its connection to the lunar calendar, Passover is a movable holiday and Easter changes its date accordingly. The First Ecumenical Council established the principle that Easter is celebrated on the Sunday after the first full moon after the vernal equinox.