The Christian calendar is a system used by many Christian denominations to organize the year around significant events in the life of Jesus Christ and the history of the Christian Church. It includes various seasons, such as Advent, Christmas, Lent, and Easter, each with its own themes and observances. The calendar is divided into two main cycles: the liturgical year, which focuses on the life of Christ, and the sanctoral cycle, which commemorates the lives of saints. The dates of these celebrations can vary among different Christian traditions, but they all share a common foundation in the teachings of Christianity.