Easter is an annual Christian holiday that celebrates the resurrection of Jesus Christ from the dead. It is considered the most important and oldest festival of the Christian Church. Easter is observed on different dates each year, as it is based on the lunar calendar. In Western Christianity, Easter falls on the first Sunday following the first full moon after the vernal equinox, which is usually between March 22 and April 25. In Eastern Christianity, Easter is celebrated on a different date, known as Pascha, which is determined using the Julian calendar.