The Romans first divided the year into 10 months, but they early adopted the Greek method of lunar and intercalary months, mak ing the lunar year consist of 354, and after ward of 355 days, leaving 10 or 11 days and a fraction to be supplied by the intercalary di vision. This arrangement, which was placed under the charge of the pontiffs, continued until the time of Casar. The first day of the month was called the calends. In March, May, July and October, the 15th, in other months the 13th, was called the ides. The ninth day before the ides (reckoning inclusive) was called the nones. The other days of the months they reckoned forward to the next calends, nones, or ides, whether in the same or the succeeding month, always including both days in the reckoning. Thus the 3d of March, according to the Roman reckoning, would be the fifth day before the nones, which in that month fell on the 7th. The 8th of January, in which month the nones happen on the 5th, and the ides on the 13th was called the 6th before the ides of January. Finally to express any of the days after the ides, they reckoned in a similar manner from the calends of the following month. From the inaccuracy of the Roman method of reckoning it appears that in Cicero's time the calendar brought the vernal equinox almost two months later than it ought to be. To check this irregu larity Julius Czsar invited the Greek astrono mer Sosigenes to Rome, who, with the assist ance of Marcus Fabius, invented that mode of reckoning which, after him who introduced it into use, has been called the Julian calendar. The chief improvement consisted in restoring the equinox to its proper place in March. For this purpose two months were inserted between November and December, so that the year 707 (46 a.c.), called from this circumstance the year of confusion, contained 14 months. In the number of days the. Greek computation was adopted, which made it The number and names of the months were kept unaltered with the exception of Quintilis, which was henceforth called, in honor of the author of the improvement, Julius. To dispose of the quarter of a day it was determined to intercalate a day every fourth year between the 23d and 24th of February. This was called an intercalary day, and the year in which it took place was called an intercalary year, or, as we term it, a leap year.
This calendar continued in use among the Romans until the fall of the empire, and throughout Christendom till 1582. The festivals of the Christian Church were determined by it. With regard to Easter, however, it was neces sary to have reference to the course of the moon. The Jews celebrated Easter (that is, the Passover) on the 14th of the month Nisan (or March); the Christians in the same month, but always on a Sunday. Now, as the Easter of the Christians sometimes coincided with the PassoVer of the Jews, and it was thought un christian to celebrate so important a festival at the same time as the Jews did, it was re solved at the Council of Nice, 325 A.D., that from that time Easter should be solemnized on the Sunday following the first full moon after the vernal equinox, which was then supposed to take place on 21 March. As the course of the moon was thus made the foundation for determining the time of Easter, the lunar Cycle of Meton was taken for this purpose; accord ing to which the year contains 365% days, and the new moons, after a period of 19 years, return on the same day as before. The inac
curacy of this combination of the Julian year and the lunar cycle must have soon discovered itself on a comparison with the true time of the commencement of the equinoxes, since the re ceived length of 365K days exceeds the true by about 11 minutes; so that for every such Julian year the equinox receded 11 minutes, or a day in about 130 years. In consequence of this, in the 16th century, the vernal equinox had changed its place in the calendar from the 21st to the 10th; that is, it really took place on the 10th instead of the 21st, on which it was placed in the calendar. Luigi Lilio Ghiraldi, fre quently called Aloysius Lifius, a physician of Verona, projected a plan for amending the calendar, which, after his death, was presented by his brother to Pope Gregory XIII. To carry it into execution, the Pope assembled a number of prelates and learned men. In 1577 the proposed change was adopted by all the Catholic princes; and in 1582 Gregory issued a brief abolishing the Julian calendar in all Catholic countries, and introducing in its stead the one now in use, under the name of the Gregorian or reformed calendar, or the new style, as the other was now called the old style. The amendment ordered was this: 10 days were to be dropped after 4 Oct. 1582, and the 15th was reckoned immediately after the 4th. Every 100th year, which by the old style was a leap year, was now to be a common year, the 4th century divisible by four excepted; that is, 1600 was to remain a leap year, but 1700, 1800, 1900 of the common length, and 2000 a leap year again. In this calendar the length of the solar year is taken to be 365 days, 5 hours, 49 minutes and 12 seconds, the difference between which and the true length is immaterial. In Spain, Portugal and the greater part of Italy the amendment was introduced according to the Pope's instructions. In France the 10 days were dropped in December, the 10th being called the 20th. In Catholic Switzerland, Ger many and the Netherlands the change was in troduced in the following year, in Poland in 1586, in Hungary 1587. Protestant Germany, Holland and Denmark accepted it in 1700, and Switzerland in 1701. In the German •empire a difference still remained for a considerable time as to the period for observing Easter. In England the Gregorian calendar was adopted in 1752, in accordance with an act of Parlia ment passed the previous year, the day after 2d September becoming the 14th. Sweden fol lowed in 1753. Russia and Greece still adhere to the Julian calendar, which, by the interjec tion of two more days, 1800 and 1900 being regarded as leap years, now differs from the Gregorian calendar by 13 days. Thus 14 Jan. 1917 of the new style will be 1 Jan. 1917 in Greece and Russia.
The change adopted in the English calendar in 1752 embraced another point. There had been previous to this time various periods fixed for the commencement of the year in various countries of Europe. In France, from the time of Charles IX, the year was reckoned to begin from 1 January; this was also the popular reckoning in England, but the legal and ecclesiastical year began on 25 March. The 1st of January was now adopted as the beginning of the legal year, and it was 'customary for some time to give two dates for the period intervening between 1 January and 25 March, that of the old and that of the new year, as January 1752-53.