423. Time when, or within which, is expressed by the ablative; time how long by the accusative.
on the appointed day
at what hour?
in the third watch
tribus proximīs annīs (Iug. 11)
within the last three years
Diēbus vīgintī quīnque aggerem exstrūxērunt. (B. G. 7.24)
Within twenty-five days they finished building a mound.
diēs continuōs trīgintā
for thirty days together
cum trīduum iter fēcisset (B. G. 2.16)
when he had marched three days
Note— The Ablative of Time is locative in its origin (§ 421); the Accusative is the same as that of the extent of space (§ 425).
424. Special constructions of time are the following.
a. The Ablative of Time Within Which sometimes takes in, and the Accusative of Time How Long per, for greater precision.
in diēbus proximīs decem (Iug. 28)
within the next ten days
lūdī per decem diēs (Cat. 3.20)
games for ten days
b. Duration of time is occasionally expressed by the ablative.
Militēs quīnque hōrīs proelium sustinuerant. (B. C. 1.47)
The troops had sustained the fight five hours.
Note— In this use the period of time is regarded as that within which the act is done, and it is only implied that the act lasted through the period. Cf. inter annōs quattuordecim (B. G. 1.36) for fourteen years
c. Time during which or within which may be expressed by the accusative or ablative of a noun in the singular, with an ordinal numeral.
within [just] four days
(literally on the fifth day)
The Romans counted inclusively, see § 631.d
Rēgnat iam sextum annum.
He has reigned going on six years.
d. Many expressions have in Latin the construction of time when where in English the main idea is rather of place.
pūgnā Cannēnsī (or, apud Cannās)
in the fight at Cannœ
at the Roman games
omnibus Gallicīs bellīs
in all the Gallic wars
e. In many idiomatic expressions of time, the accusative with ad, in, or sub is used. Such are the following.
Supplicātiō dēcrēta est in Kalendās Iānuāriās.
A thanksgiving was voted for the first of January.
Convēnērunt ad diem.
They assembled on the [appointed] day.
sub idem tempus
about the same time
f. Distance of time before or after anything is expressed in several different ways.
post (ante) trēs annōs
post tertium annum
trēs post annōs
tertium post annum
tribus post annīs
tertiō post annō (§ 414)
three years after
tribus annīs (tertiō annō) post exsilium
postquam ēiectus est
three years after his exile
hīs tribus proximīs annīs
within the last three years
a few years hence
abhinc annōs trēs (tribus annīs)
ante hōs trēs annōs
three years ago
Triennium est cum.
Trēs annī sunt cum.
It is three years since.
octāvō mēnse quam
the eighth month after (see § 434, Note).
g. In Dates the phrase ante diem (a.d.) with an ordinal, or the ordinal alone, is followed by an accusative, like a preposition; and the phrase itself may also be governed by a preposition. The year is expressed by the names of the consuls in the Ablative Absolute, usually without a conjunction (§ 419.a).
Is diēs erat a. d. v. Kal. Apr. (quīntum Kalendās Aprīlīs) L. Pīsōne A. Gabīniō cōnsulibus. (B. G. 1.6)
That day was the 5th before the kalends of April (March 28), in the consulship of Piso and Gabinius.
in a. d. v. Kal. Nov. (Cat. 1.7)
to the 5th day before the kalends of November (Oct. 28)
xv. Kal. Sextīlīs
the 15th day before the kalends of August (July 18)
Full form: quīntō decimō diē ante Kalendās
For the Roman Calendar, see § 631.