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The primitive divisions of time were the day (the civil day between two sunrises or sunsets), and the lunar month taken as 30 days instead of the actual 29-1/2. Twelve lunar months made a calendar year of 360 days, to which were added, in ancient Egypt, five intercalary days. The additional day required every fourth year was called by the Romans _bissextum calendis_, as it was introduced by repeating the sixth day of the calends of March (our February 24).
From the 360 calendar days of the year was derived the division of the sun’s apparent path on the ecliptic (and of every other circle) into 360 degrees. The ecliptic was divided, like the year, into twelve equal parts named from the constellations to which they corresponded; each of these was of 30 parts.
To avoid the intercalary days at the end of the ordinary year, these were afterwards distributed among the months in various ways. The number of days to each modern month is inherited, with some changes, from the arrangement adopted by a Greek-Asiatic nation. The names of the months are those given by the Romans; their year originally began with March (as indeed did ours, on Lady Day, down to 1751), and the original names were:
_Martius_ from Mars. _Aprilis_ from Aphrodite (Venus).[41] _Maius_ from _dü maiores_, the elder gods. _Junius_ from _dü juniores_, the younger gods. Quintilis the 5th month, afterwards Julius. Sextilis the 6th „ „ Augustus. Septembris the 7th „ Octobris the 8th „ Novembris the 9th „ Decembris the 10th „ Januarius from Janus or Dianus, the sun-god. Februarius from februum, the expiation month.
In the Bithynian calendar were a couple of months, _Areios_ and _Aphrodisios_ (once _Artemisios_), the Greek forms corresponding to Martius and Aprilis.
The week is of astrological origin. Even in Europe there are still many people who believe that the seven planets of the pre-Copernican system rule, each in its turn, the successive hours of each day; the planet ruling the first hour gives its name to the day, and influences it astrologically. Thus the week is the series of seven days ruled successively in the first hour by one of the seven planets. From the series of planets arranged in the order of their periods—Saturn, Jupiter, Mars, Sun, Venus, Mercury, Moon—the order of the day-names comes about in the following way: