YEAR, a division of time containing a complete course of the seasons, and depending upon the revolution of the earth (q.v.)round the sun. Its duration was variously deter mined by the nations of antiquity; the earliest method being the conventional-one of making it- include a certain number of lunar months; the lunar month being, after the day, the first period of time which was fixed. Twelve lunar months, giving a year of 354 days, were first taken as a near approach to a course of the seasons. This, though a pretty close approximation to the true value of a year, was yet so incorrect (being defective by more than 11 days) that it was soon found to be necessary to intercalate these 11 days, in order to preserve the year in a constant relative position to the seasons. The intercalation was variously effected; thus, the Egyptians, who knew the year of 365 days previous to 1500 n.c., divided it into three seasons (" winter." '` summer," and " the Nile," i.e.. the inundation, of the .Nile) of four months each, made each month con tain 30 introduced five intercalary days at the, end of the 12th month; the Greeks, who generally retained the lunar year of 354 days, added 3 months in the course of every eight years, givino. an additional month to the third fifth, and eighth year of each cycle; the Romans also added additional days, but their system of intercalation was continually changed, not always for the better, till Julius Ctesar caused the adoption of the solar year. The Romans likewise abolished, in Asia, Egypt, and all the other coun tries under their sway, the old method of reckoning by lunar years, and compelled the adoption of the Julian calendar, according to which the year was assumed to contain 365 days 6 hours. The substitution of the Gregorian calendar in the 16th c. introduced for the average length of the solar year, 365 days 5 hours 49 minutes, which differs only by a few seconds from its true value; and this small annual error, as well as the excess of the true year over the year of 365 days, is compensated for by means of a succession of leap-years (q.v.).
The time at which the year began varied much among different nations. The Car thaginians, Egyptians, Persians, Syrians, and other eastern peoples commenced their• year at the autumnal equinox, at which time the civil year of the Jews also began, though their sacred 'year was reckoned from the vernal equinox. The commencement,
of the Greek year was at the winter solstice before Meton's time, and was then changed to the summer solstice. The Romans were the first to adopt the 1st day of January as the first of the year, but their example was not followed by subsequent European nations for some time. Iu France, the commencement was Mar. 1 under the Mar. 25 under the Carlovingiaus, Easter under the Capetians, and Jan. 1 from 1564. The ecclesiastical year in Europe generally commenced on Mar. 25 (see DATE). The ancient northern nations reckoned their year from the winter solstice; the Russians, till Peter the great's time, from Sept. 1, and the same reckoning, known as the Byzantine era, was in use in the eastern empire. Of necessity, the commencement of the year among Mohammedan nations has no fixed position in relation to the sun's course or the seasons, it being invariably a lunar year. In astronomy there are several kinds of years depend ing 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 recognized 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 (see PRECESSION). Next is the sidereal 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 notation (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 perhelion (q.v.) and its return to the same position, is known as the anomalistic year, and is equivalent to 365.2595981 mean solar days, or 365 days 6 hours 13 minutes 49.3 seconds. The sidereal and anomalistic years have a merely astronomical importance.