The Liturgical Calendar and the Sky
The Church’s calendar has long been tied to the motions of the sky, because the cycle of the year has always been counted by the movements of the Sun and Moon.
Easter Is Set by the Moon
In the Western Church, Easter is celebrated on “the Sunday after the first full moon on or after the spring equinox” (the actual date is determined using tables set by the Church). As a result, the date of Easter changes every year, falling anywhere from late March to late April. This is closely connected to the Jewish Passover, which has traditionally been celebrated around the time of the spring full moon.
Measuring the Sky to Correct the Calendar
In 1582, Pope Gregory XIII reformed the calendar (the Gregorian calendar), because under the old calendar the actual spring equinox and the calendar’s equinox had drifted about 10 days apart. The calendar now widely used around the world was put in order at that time through astronomical calculation.
Advent and the Winter Night Sky
Advent is the season that includes the four Sundays before Christmas. In the Northern Hemisphere it falls around the winter solstice, when the nights are longest, and it has been kept as a time of waiting for the light in the darkest season of the year.
Today’s Calendar and Sky
- Liturgical Calendar
- Ordinary Time
- Easter
- March 28, 2027 (in 133 days)
- Christmas
- in 40 days
Moon age is an approximation based on the mean lunar cycle. The liturgical calendar shown follows the Western Church and is a general guide; reckoning differs among churches.
