The Roman Year was designated, in earlier times, by the names of the Consuls; but was afterwards reckoned from the building of the City (ab urbe conditā, annō urbis conditae), the date of which was assigned by Varro to a period corresponding with B.C. 753. In order, therefore, to reduce Roman dates to those of the Christian era, the year of the city is to be subtracted from 754: e.g. A.U.C. 691 (the year of Cicero's consulship) corresponds to B.C. 63.
Before Cæsar's reform of the Calendar (B.C. 46), the Roman year consisted of 355 days: March, May, Quīntīlis (July), and October having each 31 days, February having 28, and each of the remainder 29. As this calendar year was too short for the solar year, the Romans, in alternate years, at the discretion of the pontificēs, inserted a month of varying length (mēnsis intercalāris) after February 23, and omitted the rest of February. The “Julian year,” by Cæsar's reformed Calendar, had 365 days, divided into months as at present. Every fourth year the 24th of February (VI. Kal. Mārt.) was counted twice, giving 29 days to that month: hence the year was called bissextīlis. The month Quīntīlis received the name Iūlius (July), in honor of Julius Cæsar; and Sextīlis was called Augustus (August), in honor of his successor. The Julian year (see below) remained unchanged till the adoption of the Gregorian Calendar (A.D. 1582), which omits leap-year three times in every four hundred years.
Dates, according to the Roman Calendar, are reckoned as follows:—
The first day of the month was called Kalendae (Calends).
On the fifteenth day of March, May, July, and October, but the thirteenth of the other months, were the īdūs (Ides), the day of Full Moon.
On the seventh day of March, May, July, and October, but the fifth of the other months, were the Nōnae (Nones or ninths).
From the three points thus determined, the days of the month were reckoned backwards as so many days before the Nones, the Ides, or the Calends. The point of departure was, by Roman custom, counted in the reckoning, the second day being three days before, etc. This gives the following rule for determining the date:—
If the given date be Calends, add two to the number of days in the month preceding,—if Nones or Ides, add one to that of the day on which they fall,—and from the number thus ascertained subtract the given date. Thus,—
VIII. Kal. Feb. (31 + 2 - 8) = Jan. 25.
IV. Nōn. Mār. (7 + 1 - 4) = Mar. 4.
IV. īd. Sept. (13 + 1 - 4) = Sept. 10.
For peculiar constructions in dates, see § 424. g.
The days of the Roman month by the Julian Calendar, as thus ascertained, are given in the following table:—
The money of the Romans was in early times wholly of copper. The unit was the as, which was nominally a pound in weight, but actually somewhat less. It was divided into twelve unciae (ounces).
In the third century B.C. the as was gradually reduced to one-half of its original value. In the same century silver coins were introduced,—the dēnārius and the sēstertius. The denarius = 10 asses; the sestertius = 21/2 asses.
The Sestertius was probably introduced at a time when the as had been so far reduced that the value of the new coin (2 1/2 asses) was equivalent to the original value of the as. Hence, the Sestertius (usually abbreviated to HS or HS) came to be used as the unit of value, and nummus, coin, often means simply sēstertius. As the reduction of the standard went on, the sestertius became equivalent to 4 asses. Gold was introduced later, the aureus being equal to 100 sesterces. The approximate value of these coins is seen in the following table:—
2 1/2 asses = 1 sēstertius or nummus, value nearly 5 cents (2 1/2 d.).
10 asses or 4 sēstertiī = 1 dēnarius. value nearly 20 cents (10 d.).
1000 sēstertiī = 1 sēstertium ... value nearly $50.00 (£10).
The sēstertium (probably originally the genitive plural of sēstertius depending on mīlle) was a sum of money, not a coin; the word is inflected regularly as a neuter noun: thus, tria sēstertia = $150.00.
When sēstertium is combined with a numeral adverb, centēna mīlia, hundreds of thousands, is to be understood: thus deciēns sēstertium (deciēns HS) = deciēns centēna mīlia sēstertium = $50,000. Sēstertium in this combination may also be inflected: deciēns sēstertiī, sēstertiō, etc.
In the statement of large sums sēstertium is often omitted as well as centēna mīlia: thus sexāgiēns (Rosc. Am. 2) signifies, sexāgiēns [centēna mīlia sēstertium] = 6,000,000 sesterces=$300,000 (nearly).
In the statement of sums of money in Roman numerals, a line above the number indicates thousands; lines above and at the sides also, hundred-thousands. Thus HS DC=600 sēstertiī; HS DC= 600,000 sēstertiī, or 600 sēstertia; HS |DC|=60,000,000 sēstertiī, or 60,000 sēstertia.