Two Anchors and a Wheel of Seasons

The Christian liturgical year is built on two fixed points that move at different speeds. Christmas stands still, kept on 25 December wherever the Gregorian reckoning is followed; Easter moves, set each year by the moon, falling on the first Sunday after the first full moon on or after the spring equinox. Around these two anchors the year arranges itself into seasons.

Advent opens the cycle, four Sundays of preparation before Christmas; Christmastide flows from the feast itself; a first stretch of Ordinary Time follows; Lent then leads through forty days of penitence to Holy Week and the Paschal Triduum, the three days at the summit of the year; Eastertide keeps the fifty festal days to Pentecost; and a long second stretch of Ordinary Time carries the year back around to Advent. Each season has its own character, marked in readings, music and colour: violet for the preparatory seasons, white and gold for the great feasts, red for Pentecost and the passion, green for the ordered weeks between. The structure means no two years are identical, since the movable Easter cycle slides back and forth across the fixed calendar, shortening one stretch of Ordinary Time and lengthening the other, which is why the church's year has always needed its own tables and its own arithmetic.