Easter is a Christian festival and holiday celebrating the resurrection of Jesus Christ on the third day after his crucifixion at Calvary as described in the New Testament.  Easter is the culmination of the Passion of Christ, preceded by Lent, a forty-day period of fasting, prayer, and penance. The last week of Lent is called Holy Week, and it contains the days of the Easter Triduum, including Maundy Thursday (also known as Holy Thursday), commemorating the Last Supper and its preceding foot washing, as well as Good Friday, commemorating the crucifixion and death of Jesus. Easter is followed by a fifty-day period called Eastertide or the Easter Season, ending with Pentecost Sunday.

Easter is a moveable feast, meaning it is not fixed in relation to the civil calendar. The First Council of Nicaea (325) established the date of Easter as the first Sunday after the full moon (the Paschal Full Moon) following the March equinox.  Ecclesiastically, the equinox is reckoned to be on 21 March (even though the equinox occurs, astronomically speaking, on 20 March in most years), and the "Full Moon" is not necessarily the astronomically correct date. The date of Easter therefore varies between 22 March and 25 April. Eastern Christianity bases its calculations on the Julian calendar whose 21 March corresponds, during the 21st century, to 3 April in the Gregorian calendar, in which the celebration of Easter therefore varies between 4 April and 8 May.

Easter is linked to the Jewish Passover by much of its symbolism, as well as by its position in the calendar. In many languages, the words for "Easter" and "Passover" are etymologically related or homonymous.  Easter customs vary across the Christian world, but attending sunrise services, exclaiming the Paschal greeting, clipping the church and decorating Easter eggs, a symbol of the empty tomb, are common motifs.  Additional customs include egg hunting, the Easter Bunny, and Easter parades, which are observed by both Christians and some non-Christians.

Theological significance

The New Testament teaches that the resurrection of Jesus, which Easter celebrates, is a foundation of the Christian faith.  The resurrection established Jesus as the powerful Son of God and is cited as proof that God will judge the world in righteousness.  God has given Christians "a new birth into a living hope through the resurrection of Jesus Christ from the dead".  Christians, through faith in the working of God are spiritually resurrected with Jesus so that they may walk in a new way of life.

Easter is linked to the Passover and Exodus from Egypt recorded in the Old Testament through the Last Supper and crucifixion that preceded the resurrection.  According to the New Testament, Jesus gave the Passover meal a new meaning, as he prepared himself and his disciples for his death in the upper room during the Last Supper.  He identified the matzah and cup of wine as his body soon to be sacrificed and his blood soon to be shed. Paul states, "Get rid of the old yeast that you may be a new batch without yeast—as you really are. For Christ, our Passover lamb, has been sacrificed"; this refers to the Passover requirement to have no yeast in the house and to the allegory of Jesus as the Paschal lamb.

One interpretation of the Gospel of John is that Jesus, as the Passover lamb, was crucified at roughly the same time as the Passover lambs were being slain in the temple, on the afternoon of Nisan 14. The scriptural instructions specify that the lamb is to be slain "between the two evenings", that is, at twilight. By the Roman period, however, the sacrifices were performed in the mid-afternoon. Josephus, Jewish War 6.10.1/423 ("They sacrifice from the ninth to the eleventh hour"). Philo, Special Laws 2.27/145 ("Many myriads of victims from noon till eventide are offered by the whole people"). This interpretation, however, is inconsistent with the chronology in the Synoptic Gospels. It assumes that text literally translated "the preparation of the passover" in John 19:14 refers to Nisan 14 (Preparation Day for the Passover) and not necessarily to Yom Shishi (Friday, Preparation Day for Sabbath) and that the priests' desire to be ritually pure in order to "eat the passover" refers to eating the Passover lamb, not to the public offerings made during the days of Unleavened Bread.