Calendars and Time Reckoning

Abstract

Abstract One may regulate a calendar by means of the Sun alone, by means of the Moon alone, or by means of the Sun and Moon together. Thus, there are three principal types of calendar: solar, lunar, and luni-solar. At various times and in various cultures, all three types of calendars have been used. Indeed, all three types are still in use today. A good example of a lunar calendar is the Muslim calendar, which is still used in some countries of the Middle East, and which is used worldwide in Muslim religious practice. The most important luni solar calendar still in use is the Jewish calendar. But the ancient Greek and Babylonian calendars were also of this type. The most familiar example of a solar calendar is the Gregorian calendar, which is used nearly worldwide today. However, to reckon time reliably in astronomical and historical work, one must also understand its relation to the Julian calendar that preceded it.