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 p614  Hora

Article by Leonhard Schmitz, Ph.D, F.R.S.E, Rector of the High School of Edinburgh,
on p614 of

William Smith, D.C.L., LL.D.:
A Dictionary of Greek and Roman Antiquities, John Murray, London, 1875.

HORA (ὢρα), in the signification of hour, that is, the 12th part of the natural day, did not come into general use among the ancients until about the middle of the second century B.C. The equinoctial hours, though known to astronomers, were not used in the affairs of common life till towards the end of the fourth century of the Christian era. As the division of the natural day into twelve equal parts, both in summer and winter, rendered the duration of the hours longer or shorter according to the different seasons of the year, it is not easy, with accuracy, to compare or reduce the hours of the ancients to our equinoctial hours. The hours of an ancient day would only coincide with the hours of our day at the two equinoxes. [Dies and Horologium]. As the duration of the natural day, moreover, depends on the polar altitude of a place, our natural days would not coincide with the natural days in Italy or Greece. Ideler, in his Handbuch der Chronologie, has given the following approximate duration of the natural days at Rome, in the year 45 B.C., which was the first after the new regulation of the calendar by J. Caesar; the length of the days is only marked at the eight principal points in the apparent course of the sun.

The following table contains a comparison of the hours of a Roman natural day, at the summer and winter solstice, with the hours of our day.​a

Summer-Solstice.

Winter-Solstice.

The custom of dividing the natural day into twelve equal parts or hours lasted, as we have observed, till a very late period. The first calendarium in which we find the duration of day and night marked according to equinoctial hours, is the calendarium rusticum Farnesianum (Ideler, Handbuch der Chron. II p139, &c.; Graev. Thesaur. Ant. Rom. VIII).

Another question which has often been discussed, is whether in such expressions as prima, altera, tertia hora, &c., we have to understand the hour which is passing, or that which has already elapsed. From the construction of ancient sun-dials on which the hours are marked by eleven lines, so that the first hour had elapsed when the shadow of the gnomon fell upon the first line, it might seem as if hora prima meant after the lapse of the first hour. But the manner in which Martial (IV.8), when describing the various purposes to which the hours of the day were devoted by the Romans, speaks of the hours, leaves no doubt that the expressions prima, altera, tertia hora, &c., mean the hour which is passing, and not that which has already elapsed (Becker, Gallus, vol. I p184, &c.).

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Thayer's Note:

a A very quick and easy rule of thumb, when we read "the third hour, the sixth hour", etc., is to add 3, 6, etc. to 5:00 A.M.: The first hour, for example, runs from roughly 6 to roughly 7 A.M.; and the ninth hour from roughly 2 to roughly 3 P.M.

Parenthetically here, the hour usually mentioned as that of the death of Jesus, 3 P.M., is at the end of the ninth hour — but the Gospels say nothing about that, rather just "the ninth hour": two‑thirty would be a better approximation.

More generally and more accurately, to find what time is meant in a Greek or Roman text, for any given place — not just Rome and the dates of the solstices as given above — use the U. S. Navy's calculator to get the times of sunrise and sunset for that place, divide the difference by 12, multiply by the ordinal (minus 1) of the hour given in the ancient source, and add to the time of sunrise: you'll have the beginning of that hour.

Notice that though the date during the year is important, the year itself matters very little; roughly stated, the times of sunrise and sunset oscillate within a range of about 4 minutes over a 4‑year cycle. In practice, that means you can use the current year in the calculator; but if you don't know what the date was, you might as well use the two tables above, which will give you the outside limits.

On the other hand, our dictionary article does well to remind us that all of this goes out the window for dates before Caesar's calendar reform, since the civil date gives no real clue as to the season of the year, which of course is what matters in determining the times of sunrise and sunset.

Now for an example; the death of Augustus:

1. The year is given by "the consul­ship of Sextus Pompeius and Sextus Appuleius". Ignore it: the fluctuations of sunrise and sunset from year to year are very slight.

2. The date is "the fourteenth day before the Kalends of September", or August 19th.

3. The place is Nola: the town still exists, by the same name; it's at 40°55N 14°31E.

4. Inputting this information in the U. S. Navy calculator, and "1 hour E of Greenwich" for the time zone, we get

   Sunrise: 0516h

   Sunset: 1854h

5. The length of daylight (at Nola, on August 19th) was therefore 13h 38m, and the length of the Roman hour on that day was 1⁄12 of that, or 68⅙ (equinoctial) minutes.

6. The "ninth hour" means that (9‑1) hours had elapsed, or in equinoctial time, 8 × 68⅙ minutes = 9 hours and 5 minutes. Adding that to 0516h the time of sunrise, the beginning of the ninth hour was 1421h. The tenth hour started 68 minutes later, at 1529h: Augustus died between 2:21 and 3:29 P.M., GMT+0100.

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