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:

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:

Sunday (dies Solis) was so named from the Sun ruling its first hour. The following six hours being ruled by the other planets, the Sun again rules the eighth hour, also the fifteenth and the twenty-second; the twenty-third hour is ruled by the next planet in the series, Venus;^[42] the twenty-fourth by Mercury, and the first hour of the next day by the Moon, hence this will be Monday (dies LunÆ). The Moon ruling the first, eighth, fifteenth, twenty-second hours of Monday, the twenty-third hour will be ruled by Saturn (beginning the series again), the twenty-fourth by Jupiter, and the first hour of the next day by Mars; hence this day will be dies Martis or Tuesday, from the planet Tiw = Mars. And so on with the remaining days, the names of the planet ruling the next day being obtained by passing over the name of the two planets ruling the twenty-third and twenty-fourth hours. Thus beginning with the first planet of the series we get:

Latin Christianity made only two changes: d. dominicus for Sunday, and d. sabbati for Saturday; but the latter still retains its old name in several countries, thus:

The unit of time is the mean solar-day, the time between the noons of two successive days, noon being taken as the moment of the passage of the sun over the local meridian, corrected by the equation of time or daily correction required to reduce the varying solar days to a mean of all the solar days. So ‘mean time’ is that of a well-regulated clock dividing the year into mean solar-days of 24 hours; there being 365 days, 5 hours, 48 minutes, 46 seconds, in the astronomical year.

It is probable that everywhere, in primitive times, both day and night would be divided, in southern countries at least, or at the equinoxes, into three watches of fairly equal length: the morning, midday, afternoon; and the evening, midnight and dawn. Each of these would become divided, with the rise of astronomical observations and the use of sun-dials, into fourths, making twelve hours for either day or night; twelve hours corresponding to the twelve months of the year or to the uncial divisions of other measures. The civil day would thus be of twenty-four hours, grouped into watches of four hours or into the eight canonical divisions of the day. In medieval times midday was properly the hour of sexte, the sixth hour from prime, the third from tierce; but in course of time the ninth hour, nones, was shifted from 3 P.M. to midday, which thus became ‘noon.’

But the original division of the day, probably ChaldÆan, was strictly sexagesimal. It was divided into 60 parts (= 24 minutes), each part into 60, and this again into 60.

In medieval times the Sun’s daily path was divided into 24 hours, each of 15 degrees; and each hour was also divided into 3 miles or mileways of 5 degrees (= 20 minutes). This division was connected with the popular concrete idea of time in which 20 to 24 minutes was the common unit. In India the popular unit is still the time required to boil a pot of rice (20 to 24 minutes) or do some similar domestic task. In the Middle Ages the Western unit was the time required to walk a mile, on medieval roads.

‘And thogh I stonde there a myle’ (Gower, 1390).

‘And maketh every minute seem a myle’ (Spenser, 1594).

Then the degree was divided sexagesimally into 60 minutes each of 60 seconds, as at present. These divisions were at first called scruples, from the above-mentioned division of the day into 60 scruples of 24 minutes (the ounce being divided into scruples each of 24 light grains). Here the scruple-sense of 1/24 passes to 1/60.

‘1610. The latitude fiftie degrees and fortie scruples or minutes’ (Quot. N.E.D.).

The hour was also divided similarly into 60 scruples or minutes, each of 60 second scruples or seconds.

The ounce and scruple division of time is shown in the following passage from ‘Le Breviari d’Amor,’ a thirteenth-century poem by Ermengaud, a monk of Beziers. I have freely translated it from the Languedocian. ‘The day is divided into quarters, each of 6 hours; and the fourth part of an hour is a point, the tenth part of which is a moment; the moment is divided into 12 parts called ounces, and each of the ounces yields 47 atoms, which time called an atom cannot be further divided.’ It seems almost certain that ‘atomus xlvij’ is either a mistake for xlviij or deliberately put for set (7), to rime with ret (yields). The ounce of time, = 7-1/2 seconds, would be divided into 24 scruples and 48 oboli, called atoms as being the end of the division. Similar dropping of a unit from Roman numerals is to be found in medieval Acts of Parliament and Ordinances.

The Lunar Year

In the lunar year used by Moslems and Jews, and also recognised by law in the movable date of Easter and some other feasts, the month is approximately of 29-1/2 days, so that the year is 354 days, less than the solar year by 11 days, or 12 in leap years. Hence Moslem feasts or fasts, such as the RamadÁn and the times of pilgrimage, are that number of days earlier each year.

The age of the Moon is found by the Epact, its age on the first day of the year. It is about the same on March 1 as on January 1, owing to January and February being together equal to two lunar months. So the increase of the Epact during the year, at the rate of about one day in the month, begins March 1; and September is, for this purpose, the seventh month.

To the day of the month add the Epact and the number of the month, beginning March 1. The total, over 0 or over 30, is the age of the moon.

Example.—September 10, 1910 (7th Month), Epact for 1910 being xix.

10 + 19 + 7 = 36. The Moon was 6 days old.

What will be the date of full moon, its fifteenth day, in November 1912? November is the ninth month and the Epact for 1912 is xi.

11 + 9 = 20. 45 (= 30 + 15) - 20 = 25. Ans. November 17.

Agriculturists who believe that certain seeds should be sown, trees planted, and pigs converted into bacon during the waxing of the moon, while trees are felled during the waning, find the Epact useful in reckoning the moon’s age. It is also useful in calculating whether country-roads will be moonlit during certain nights.

The Epact increases 11 days annually: 1911, 0; 1912, xi; 1913, xxij; coming back to 0 in 31 years.

The Compass Card

While the circle of the horizon is divided into 360 degrees for astronomy and for accurate navigation, the steersman has always divided it sexdecimally. The temple of the Winds at Athens was octagonal; and the points of the horizon were named after the eight winds, a number increased to sixteen about the time of Ptolemy. The Romans tried in vain to substitute an uncial division; their 12 winds and points could not supersede the 8 winds and points of the Greeks. And to this day in the Mediterranean there are 8 principal points, named after the sun and winds:

Tramontano, Levant, Mezzodi, Ponente.

Greco, N.E.; Scirocco, S.E.; Libeccio, S.W.; Maestralo, N.W.

Amerigo Vespucci sailed for the ‘Ponente una quarta di Libeccio,’ West, one point S.W.; and afterwards for the ‘Libeccio una quarta del Mezzodi,’ S.W. one point S.