Romulus divided the year into ten months; the first of which was called March from Mars, his supposed father; the 2d April, either from the Greek name of Venus, (Aφροδιτα) or because trees and flowers open their buds, during that month; the 3d, May, from Maia, the mother of Mercury; the 4th, June, from the goddess Juno; 5th, July, from Julius CÆsar; 6th, August, from Augustus CÆsar; the rest were called from their number, September, October, November, December.Numa added two months—January from Janus, and February because the people were then purified, (februabatur) by an expiatory sacrifice from the sin of the whole year: for this anciently was the last month in the year.

Numa in imitation of the Greeks divided the year into twelve lunar months, according to the course of the moon, but as this mode of division did not correspond with the course of the sun, he ordained that an intercalary month should be added every other year.

Julius CÆsar afterwards abolished this month, and with the assistance of Sosigĕnes, a skilful astronomer of Alexandria, in the year of Rome 707, arranged the year according to the course of the sun, commencing with the first of January, and assigned to each month the number of days which they still retain. This is the celebrated Julian or solar year which has been since maintained without any other alteration than that of the new style, introduced by pope Gregory, A. D. 1582, and adopted in England in 1752, when eleven days were dropped between the second and fourteenth of September.

The months were divided into three parts, kalends, nones and ides. They commenced with the kalends; the nones occurred on the fifth, and the ides on the thirteenth, except in March, May, July, and October, when they fell on the seventh and fifteenth.

In marking the days of the month they went backwards: thus, January first was the first of the kalends of January—December thirty-first was pridie kalendas, or the day next before the kalends of January—the day before that, or the thirtieth of December, tertio kalendas Januarii, or the third day before the kalends of January, and so on to the thirteenth, when came the ides of December.

The day was either civil or natural; the civil day was from midnight to midnight; the natural day was from the rising to the setting of the sun.

The use of clocks and watches was unknown to the Romans—nor was it till four hundred and forty-seven years after the building of the city, that the sun dial was introduced: about a century later, they first measured time by a water machine, which served by night, as well as by day.

Their days were distinguished by the names of festi, profesti, and intercisi. The festi were dedicated to religious worship, the profesti were allotted to ordinary business, the days which served partly for one and partly for the other were called intercisi, or half holy days.

The manner of reckoning by weeks was not introduced until late in the second century of the christian era: it was borrowed from the Egyptians, and the days were named after the planets: thus, Sunday from the Sun, Monday from the Moon, Tuesday from Mars, Wednesday from Mercury, Thursday from Jupiter, Friday from Venus, Saturday from Saturn.