New Testament
A Liturgical Calendar is a Calendar of Remembrance. It is based on the Jewish year of feasts. The Jews used the moon-calendar. Israel had predetermined days for their feasts: the Sabbath, Passover, Feast of Tabernacles, Day of Atonement, Year of Jubilee, each with their specific ceremonies. Following this, the New Testament church after Pentecost celebrates the weekly Sunday, Good Friday, Easter (with a fixed date, 14 Nisan), etc.
In our Western culture, we follow the Sun-year (Gregorian calendar). This means that Easter and Pentecost are on a different date each year (e.g. Easter is the first Sunday in the Spring after a full moon).
These feasts in Israel were milestones on the road to the fulfilling of Gods promises. There is a direct relation is every feast with the acts of God (Passover. Feast of Tabernacles, Day of Atonement) and with the seasons (Pentecost) or both (Feast of Tabernacles - the journey through the desert - the grape Harvest). These feasts point to fulfillment of Gods promises, time and again. The people that celebrate these feasts, do not only remember Gods great deeds from the past, but also live in expectation of Gods action today and in the future.
The New Testament church followed in the footsteps of the church of the Old Testament. Remembering has the same meaning as in the Old Testament, but our Lord has risen from the dead! What is coming: the marriage feast of the Lamb! The center of the church year of remembering is Easter. Every Sunday is a little echo of this celebration. Throughout the years, a number of days of remembering before and after Easter was called the Circle of Easter. This is from the 40 days before Easter (from Ash Wednesday) to the day of Pentecost. This period is called Lent.
Christmas became also an important feast to celebrate In later Centuries. Also around Christmas developed a circle of remembering: Advent starts four Sundays before Christmas and Epiphany (revelation of the Lord) is January 6. Sundays in between Christmas and Easter and in between Easter and Christmas were given their own place in remembering and looking forward in the liturgical calendar.
The Christian liturgical calendar starts with Remembering: Gods plan of salvation through Jesus Christ, his Son, its execution and its completion. In order to keep this fresh in our memory, God wants us to celebrate, on Sundays and on special feast days. And therefore we see the circle of celebration and feasts year round, with Scripture readings, prayers, and church songs selected for that particular purpose.