The Church calendar is also called the “Liturgical Calendar.” It has been the traditional practice of civilized peoples to have the cycle of the times of the year associated with their religious practices.
This has been true of the Jewish calendar, the calendar of the Muslims, which began with the year 1 corresponding to the year A.D. 622, as well as, the Chinese and Japanese calendars.
The early Church Calendar followed the time cycles of twelve lunar months, amounting to 364 days in the year, but this was incorrect and could not be brought into proper reckoning with the Julian calendar.
There were inaccuracies in the Julian calendar in calculating the length of the year and this error, amounting to ten days by 1582, was corrected by the Gregorian calendar under the urging of Pope Gregory the XIII. The accumulated error of ten days was eliminated, and the slight astronomical difference was corrected by the new reckoning of leap year.
The Church Calendar is an arrangement of a series of liturgical seasons throughout the year and a daily assignment of feasts of the saints.
There is unity and harmony in this procedural course of integrating each day of the year into a continuing, interrelated cycle of divine worship that takes into account both the daily celebration of the Eucharist and the Liturgy of the Hours. (7:51)