CALENDAR (Lat. ealendarium. account book, interest falling due on the calends, from ealcnda% calends). The mode of adjusting the months and other divisions of the civil year to the natural Or solar year. The necessity of some division and measurement of time must have been early felt. The phases or changes of the moon supplied a natural and very obvious mode of dividing and reckoning time, and hence the division into months (q.v.; see also WEEK) of 29 or 30 days was, perhaps. the earliest and most universal. But it would soon be observed that, for many purposes, the changes of the sea sons were more serviceable as marks of division; and thus arose the division into years (q.v.), determined by the motions of the sun. It was soon, however, discovered that the year, or larger division, did not contain an exact num ber of the smaller divisions or months, and that an accommodation was necessary; and various not very dissimilar expedients were employed for correcting the error that arose. The ancient Egyptians had a year determinc I 1 by the changes of the seasons, without reference to the changes of the moon, and containing 365 days, divided into twelve months of :30 days each, with five supplementary (lays at the end of the year. The Jewish year consisted, in the earliest periods, as it still does, of twelve lunar months, a thir teenth being from time to time introduced, to accommodate it to the sun and seasons. This was also the case with the ancient Syrians, Macedonians, etc. The Jewish months have al ternately 29 and 30 days; and in a cycle of 19 year there are 7 years having the intercalary month, some of these years having also one, and some two days more than others, so that the length of the year varies from 353 to 3S5 The Greeks, in the most ancient periods, reek cned according to real lunar months, twelve making a year; and about n.c. 594 Solon intro duced in Athens the mode of reckoning alter nately 30 and 29 days to the month, accommo dating this civil year of 354 days to the solar year by occasional introduction of an interealary mouth. A change was afterwards made. by which three times in 8 years a month of 30 days was intercalated, making the average length of the year 365% days. See METONIC CYCLE.
The Romans are said to have had originally a year of 10 months; but in the time of their kings they adopted a lunar year of 355 days, divided into 12 months, with an occasional inter calary month. Through the ignorance of the priests, who had the charge of this matter, the utmost confusion gradually arose. which .Tulius (:psar remedied I n.c. -16) by the introduction of the Julian Calendar, according to which the year Las ordinarily 365 days, and every fourth year is a leap year of 366 days—the length of the year being thus assumed as days, while it is in reality 365 days, 5 hours, 48 minutes, and 4ti seconds; or 11 minutes, 14 seconds less. Cwsar gave the months the number of days they still have. See KALEN DS.
So perfect was the .Julian style of reckoning that it prevailed generally among Christian na tions, and remained undisturbed till the accumu lation of the remaining error of 11 minutes or so had amounted, in 1582, to 10 complete days, the vernal equinox falling on the 1 lth instead of the 21st of March, as it did at the time of the Council of Nice, A.D. 325. This shifting of days had caused great disturbances. by 'infixing the times of the celebration of Easter, and hence of all the other movable feasts, and ac cordingly, Pope Gregory XIII., after careful study, with the aid of Clavius, the astronomer, ordained that 10 days should lie deducted from the year 1582, by calling what, according to the old calendar, would have been reckoned the 5th of October the 15th of October, 1582: and, in order that this displacement might not recur. it was further ordained that every hundredth year (1800. 1900, 2100, etc.) should not be counted a leap year, excepting every fourth hun dredth, beginning with 2000. In this way the difference between the civil and natural year will not amount to a day in 5000 years. In Spain, Portugal, and part of Italy. the Pope was exactly obeyed. In France the change took place in the same year, by calling the 10th the 20th of December. In the Countries the change was from the 15th December to the 25th; but it was resisted by the Protestant part of the community till the year 1700. The Catho lic nations, in general, adopted the style or dained by their sovereign pontiff; but the Pro testants were then too much inflamed against Catholicism in all its relations to receive even a purely scientific improvement from such hands. The Lutherans of Germany, Switzer land, and, as already mentioned, of the Low Countries, at length gave way in 1700, when it had become necessary to omit 11 instead of 10 days. A bill to this effect had been brought be fore the Parliament of England in 158,5, but does not appear to have gone beyond a second reading in the Ilouse of Lords. It was not till 1751, and after great inconvenience had been experienced for nearly two centuries, from the difference of the reckoning. that an act was passed (24 Geo. IL, 17511 for equalizing the style in Great and Ireland with that used in other countries of Europe. It was then enacted that 11 clays should he omitted after the 2d of September, 1752, so that the ensuing day should he the 14th. A similar change was about the same time made in Sweden and Tus cany, and Russia is now the only country which adheres to the old style: an adherence which renders it necessary, when a letter is thence ad dressed to a person in another country. that the date should be given thus: April .fogy vl927 It will be observed that the years 1800 and 1900, not being considered by us as leap have interjected two more days, making the dif ference thirteen days between old and new style.