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| The
Evolution of Calendars |
| Page 2 |
| Greek Calendar: By 13th century B.C. Greeks were using lunar calendar based on the visible new crescent. Later they also learnt intercalation to bring lunar calendar in phase with seasons and started using lunisolar calendar. Astronomers such as Maton in 432 B.C. calculated a 19-year lunisolar cycle where moon phases would repeat in the same seasons. This was called "Metonic Cycle" where 19 solar years were equal to lunar 19 years and 7 months. This concept was later adopted by Jewish or Hebrew calendar. Hebrew Calendar: Hebrew Calendar, promulgated by the Patriarch, Hillel II, in the mid-fourth century is a lunisolar calndar with months based on new crescent moon but adding a 13th month every so often to bring their lunisolar calendar in phase with the seasons. It consists of 12 month in a common year and 13 months in a leap year. Leap years occur seven times in a cycle of 19 years (Metonic cycle), such that 3rd, 6th, 8th, 11th, 14th, 17th, and 19th year are leap years. Common years may have 353-355 days, while leap years may have 383-385 days. The beginning of the Hebrew new year is determined by the occurrence of the new moon (conjunction) of the seventh month (Tishri), subject to possible postponement of a day or two according to some rules. Roman Calendar: About seven hundred years before Julius Caeser, Romans were observing some nominally lunar calendar, and were adding days or a 13th month at the end of their calendar year to keep their calendar in phase with seasons.
The new year used to begin on March 15, which was the date when new consul took office. In 153 B.C. the beginning of the year was changed to January 1. This was carried over into the Julian calendar. Julian Calendar: Following his conquest of Egypt in 48 B.C. Roman Emperor, Julius Caeser consulted the Alexandrian astronomer Sosigenes about calendar reform. Caeser adopted the calendar identical to the Alexandrian Aristarchus' calendar of 239 B.C., that consisted of a solar year of 12 months and of 365 days with an extra day every fourth year. This was a truly solar calendar and was later called, "Julian Calendar" named after him. Month lengths were extended to 30 or 31 for different months to bring the calendar's total to 365 with an addition of an extra day every fourth (leap) year to account for the true length of the solar year more close to 365.25 days. By the year 46 B.C. it was noticed that the spring equinox had shifted by about 2 months coming in May. Caeser wanted to bring spring equinox into correct position of Martius (March) 21. The year 46 B.C. is regarded as the "year of confusion" by modern authors, because in that year two intercalations were done; one to correct for spring equinox and the other to change lunisolar calendar to purely solar calendar resulting in the length of that year to 445 days. The following year i.e., 45 B.C. the Julian Calendar looked like this:
Caeser was assassinated in 44 B.C. and the month Quintilis was later renamed as Julius (July) to honor him. Soon after Caesar's assassination, his nephew and adopted son Octavian became the emperor that we refer to as "Augustus," an honorary title that had been bestowed upon him. For a time after his death, priests in charge of the calendar erroneously inserted an extra day every three years instead of every four. As a result, this caused the calendar to again drift away from the seasons, an error that needed correction. In 8 A.D. Octavian found it necessary to readjust the calendar. To eliminate the effect of this extra intercalation, leap years were discontinued from about 9 B.C. until 8AD. The leap years were: 45BC, 42BC, 39BC, 36BC, 33BC, 30BC, 27BC, 24BC, 21BC, 18BC, 15BC, 12BC, 9BC, 8AD, 12AD and every 4th year from then on. |
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