Easter, which celebrates Jesus Christ’s resurrection from the dead, is Christianity’s most important holiday. It has been called a moveable feast because it doesn’t fall on a set date every year, as most holidays do.

Instead, Christian churches in the West celebrate Easter on the first Sunday following the full moon after the vernal equinox on March 21. Therefore, Easter is observed anywhere between March 22 and April 25 every year. Orthodox Christians use the Julian calendar to calculate when Easter will occur and typically celebrate the holiday a week or two after the Western churches, which follow the Gregorian calendar.

The exact origins of this religious feast day’s name are unknown. Some sources claim the word Easter is derived from Eostre, a Teutonic goddess of spring and fertility. Other accounts trace Easter to the Latin term hebdomada alba, or white week, an ancient reference to Easter week and the white clothing donned by people who were baptized during that time.

Jesus’ crucifixion and resurrection occurred after he went to Jerusalem to celebrate Passover (or Pesach in Hebrew), the Jewish festival commemorating the ancient Israelites’ exodus from slavery in Egypt.

Easter is really an entire season of the Christian church year, as opposed to a single-day observance.

Lent, the 40-day period leading up to Easter Sunday, is a time of reflection and penance and represents the 40 days that Jesus spent alone in the wilderness before starting his ministry, a time in which Christians believe he survived various temptations by the devil.

The day before Lent, known as Mardi Gras or Fat Tuesday, is a last hurrah of food and fun before the fasting begins.

Holy week, or the week preceding Easter, includes Maundy Thursday, which commemorates Jesus’ last supper with his disciples; Good Friday, which honors the day of his crucifixion; and Holy Saturday, which focuses on the transition between the crucifixion and resurrection. The 50-day period following Easter Sunday is called Eastertide and includes a celebration of Jesus’ ascension into heaven.

Easter is the most sacred of holidays for Christians because the entire basis of Christianity is founded in the belief that Jesus, the son of God, was born to live among men and women and to sacrifice His life so that those who believe in Him will have eternal life.

During Easter, Christians celebrate the resurrection of Jesus — a testament to the awesome power of God and unconditional mercy and forgiveness for human beings who, while made in the image of God, are imperfect creatures.

It is because of Christ’s birth, life, sacrificial death and resurrection from the dead that people who believe in, accept the teachings of and make the conscious choice to follow Jesus, will also defeat death by being given the gift of eternal life in Heaven with God the Father and Christ the Son.

It is the Biblical events leading up to and culminating in the Christian celebration of Easter Sunday that provide significance to this holiday for those who ascribe to the fundamental beliefs of Christianity.