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GREGORIAN CALENDAR |
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Since the ancient times, people has been interested in marking time. Thru knowledge of the positions of the sun and the stars, as well as seasonal events, the length of a year may be computed. The length of a year is approximately 365.2425 days. The Julian Calendar, developed during the time of Julius Ceasar, was based on the approximation that the length of year was 365.25 days. Thus, every 4 years, an extra day was needed to compensate for the extra time needed to fully complete the period of earth's revolution around the sun. Because the approximation used for the Julian calender year was 365.25, instead of the more accurate number of 365.2425, every one hundred year on the Julian Calendar introduces an unnecessary extra leap day on the calendar. This causes inaccuracy in prediction the Spring Equinox, which is important in the determination of the date of Easter. These small inaccuracies added up over the centuries, and caused the celebration of Easter to occur at a later time in spring. The Gregorian Calendar was introduced in 1582, when Pope Gregory XIII modified the Julian calendar. The purpose of this modification was to restore the date of Easter to spring. Unlike the Julian Calendar, the years divisible by 100 in the Gregorian Calendar are not leap years, unless they are divisible by 400. Thus, the years 1700, 1800 and 1900 were not leap years, while the years 1600 and 2000 were.
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