Menologion in the context of "Tetraptych"

The calendar of saints is the traditional Christian method of organizing a liturgical year by associating each day with one or more saints and referring to the day as the feast day or feast of said saint. The word "feast" in this context does not mean "a large meal, typically a celebratory one", but instead "an annual religious celebration, a day dedicated to a particular saint".

The system rose from the early Christian custom of commemorating each martyr annually on the date of their death, their birth into heaven, a date therefore referred to in Latin as the martyr's dies natalis ('day of birth'). In the Eastern Orthodox Church, a calendar of saints is called a Menologion. "Menologion" may also mean a set of icons on which saints are depicted in the order of the dates of their feasts, often made in two panels.

The Menologion, Menologium, or Menology of Basil II is a Greek illuminated manuscript designed as a church calendar or Eastern Orthodox Church service book (menologion) that was compiled c. 1000 AD for the Byzantine Emperor Basil II (r. 976–1025). It contains a synaxarion, a short collection of saints' lives, compiled at Constantinople for liturgical use and around 430 miniature paintings by eight different artists. It was unusual for a menologion from that era to be so richly painted. It currently resides in the Vatican Library (Ms. Vat. gr. 1613).A full facsimile was produced in 1907.