Year.

Year. The origin of this division of time, its duration, and the history of its changes are discussed under CALENDAR. For the ecclesiastical year, which in Europe generally commenced on 25th March, see CHRONOLOGY. In Astronomy there are several kinds of years depending upon the various configurations of the earth in its orbit, and consequently varying in length. First there is the tropical or (as it is sometimes incorrectly called) solar year, which, from its being recognised in legislation and history, and commonly applied in the measure of time, has also received the name of civil year. This year is defined as the time which elapses from the sun's appearance on one of the tropics to its return to the same, and has a mean length of 365.2422414 mean solar days, or 365 days 5 hours 48 minutes 49.7 seconds. Next is the sideral year, which is the period required by the sun to move from a given star to the same star again, and this year, affected as it is by Nutation (q.v.) only, is one of the most invariable quantities which nature presents us with, and has a mean value of 365.2563612 mean solar days, or 365 days 6 hours 9 minutes 9.6 seconds. The time which elapses between the earth's arrival at its Perihelion (q.v.) and its return to the same position is known as the anomalistie year, and is equivalent to 365.2595981 mean solar days, or 365 days 6 hours 13 minutes 49.3 seconds. The canicular year—the ancient Egyptian—was counted from one heliacal rising of Sirius to the next. The canicular cycle was the cycle of 1461 years of 365 days each, or 1460 Julian years, also called the Sothic period.