The Sumerians of Babylonia were probably the first people to make a calendar. They used the phases of the moon, counting 12 lunar months as a year. To make up for the difference between this year and the year of the seasons, they inserted an extra month in the calendar about every four years. The early Egyptians, Greeks, and Semitic peoples copied this calendar. Later the Egyptians worked out a calendar that corresponded almost exactly to the seasons.
The early Romans also used a calendar that was based on the moon. The year in this calendar was 355 days long. The months corresponding to March, May, July, and October each had 31 days; February had 28 days; and the rest had 29. An extra month was added about every fourth year.
The high priest regulated the calendar. On the calends, or day of the new moon, he announced to the people the times of the nones (first quarter) and ides (full moon) for that month. The word calendar is from the Latin word kalendae.
The priests, however, performed their calendar-keeping duties poorly, and by Julius Caesar's time they had summer months coming in the spring. Caesar corrected this situation in 46 BC in the Julian calendar. He adopted the plan of the Egyptian astronomer Sosigenes--a 365-day year, with one day added every fourth, or "leap," year. He distributed the extra ten days among the 29-day months, making them identical with the months today.
The month Quintilis was renamed July for Julius Caesar. Later Sextilis was renamed August in honor of Emperor Augustus. An old story tells how Emperor Augustus changed the number of days in his month from 30 to 31 so that it would be as long as Caesar's. The story probably has no basis in fact.
Julius Caesar's correction of one day in four years (1/4 day, or six hours, a year) made the calendar year longer than the year of the seasons. Thus anniversaries began coming earlier and earlier in the year. In 1582 the vernal equinox, or beginning of spring, occurred on March 11 instead of the correct date, March 21.
Pope Gregory XIII remedied this by directing that ten days be dropped from the calendar and that the day after Oct. 4, 1582, should be October 15. He also directed that three times in every 400 years the leap-year arrangement should be omitted.
The new calendar was called the Gregorian, or New Style (N.S.), calendar. It was adopted by Roman Catholic countries, but Protestant and Eastern Orthodox countries long continued to use the Old Style (O.S.), or Julian, calendar. The new calendar was not adopted in England until 1752, when it was necessary to drop 11 days. The Eastern Orthodox church accepted the New Style in 1923, when 13 days were "lost." The Chinese had adopted it in 1912.
Another reform that the Gregorian calendar effected was general adoption of January 1 as the beginning of the year. Until then some nations began it with December 25, others with January 1 or March 25 (as England did before 1752).
Posted: 23 Sep 2009