Refers to the principal festival and feast of the Christian church in which the resurrection of Jesus Christ is celebrated. In Western churches it is observed between March 22 and April 25 depending on the date of the first full moon after the vernal equinox. Orthodox churches use the Julian date for the equinox and so usually celebrate Easter on a different, later date. The name may derive from 'Eostre,' the name of an Anglo-Saxon spring goddess. Some traditions associated with Easter (e.g. Easter eggs, the Easter rabbit) have pagan origins. Easter evolved from the primitive Christian feast known as the Pasch of the 2nd and 3rd centuries; it was the Christian counterpart to the Jewish festival of Passover and it commemorated both Christ's death and Christ's resurrection. The paschal vigil is the main celebration of Easter in liturgical churches and is held on the night before; the paschal candle was introduced in about the 4th century. While the festival of Easter occurs on one particular Sunday, its importance is emphasized by the long preparation of Lent, by the solemn services of Holy Week, and by the following fifty days until Pentecost, a period known as Eastertide or Paschaltide. Easter's importance is reflected in the fact that the entire liturgical year of worship is arranged around it, as is the ecclesiastical calendar of movable feasts. There are many allusions to baptism in Easter services, reflecting the early practice of baptizing catechumens during the vigil.