The Christian liturgical calendar is a system of commemorating key events and figures in the life of Jesus Christ, as well as other saints and important dates in the history of the Church. The earliest form of the Christian calendar was based on the Jewish liturgical calendar, which marked important festivals and holy days such as Passover and Yom Kippur. However, as Christianity developed and established their community and liturgy, the use of Christian liturgical calendar superseded the Jewish liturgical life. Likewise, the holy day for rest and worship of Sabbath was replaced by the first day of the week (Sunday), which has been known as the Lord's Day because Jesus was resurrected on the Sunday.
The key importance is the participation and celebration of Christian life in the new covenant established by Jesus Christ instead of the Hebrew and Jewish old covenantal life.
Our Christian faith proclaim Jesus Christ as the fulfilment of Hebrew prophecy and he is the Lamb of God, perfect sacrifice for the forgiveness of sins. Therefore, the Christian calendar prioritized events in the life of Jesus, such as his birth, death, resurrection, ascension, and post-ascension (Pentecost) rather than the Jewish festivals and holy days. The Christian calendar also introduced new feasts and observances, such as Christmas and Easter/Paschal, which were not based on the Jewish calendar.
Another reason for the separation of the Christian and Jewish calendars was the growing tension between the early Church and the Jewish religious establishment. As Christianity spread throughout the Roman Empire during the first century, it came into conflict with Judaism, which was viewed as a rival and often persecuted by the authorities. The Christian Church sought to distance itself from Judaism in order to establish its own identity and legitimacy as a separate religion.
Today, the Christian liturgical calendar is widely used by orthodox Christian churches around the world. Anglicans, Eastern Orthodox, Roman Catholic, Lutherans, Methodists, and Presbyterians follow the pattern and life of Jesus Christ in the liturgical calendar. It serves as a way to organize worship, prayer, and reflection around key events in the life of Jesus and the history of the Church. While the Jewish calendar continues to be observed by Jewish communities around the world, the Christian calendar has become the dominant system of marking time in the Western world, and it has had a profound impact on art, literature, and culture.
Read about why Christians should not follow Judaism in this article.