1. Term
The word calendar derives from the name of the first day of the month in Ancient Rome (Latin Kalendae). From Latin kalendarium (‘debt-book’), it later came to refer to the whole system of reckoning time (Time, reckoning of). All known calendars are based on the alternation of day and night, the recurrent phases of the Moon (OE mona = “Moon”; monađ = “month”), and the course of …