Easter, or Resurrection Day, is the most important religious feast in the Christian liturgical year.  It celebrates the resurrection of Jesus, which Christians believe occurred on the third day after his crucifixion some time in the period AD 27 to 33.  Many pagan elements have become part of the celebration, and those aspects are often celebrated by many Christians and non-Christians alike.  Easter also refers to the season of the church year called Eastertide or the Easter Season.  Traditionally, the Easter Season lasted for the forty days from Easter Day until Ascension Day but now officially lasts for the forty days until Pentecost.  The first week of the Easter Season is known as Easter Week or the Octave of Easter.