The accusative of extent of time answers “for how long?” or “through how much time?” It measures an event or state along a temporal span: trēs hōrās exspectāvī “I waited for three hours.” English normally inserts “for,” but Classical Latin can express the measurement with the bare accusative because the case itself marks extent.
Duration, not location in time
The central contrast is between duration and time when:
| Question | Latin construction | Example |
|---|---|---|
| How long? | Accusative of extent | trēs hōrās “for three hours” |
| When? | Ablative of time when | tertiā hōrā “at the third hour” |
| Within what period? | Ablative of time within which | tribus hōrīs “within three hours” |
Trēs hōrās ante portam exspectāvimus.
We waited in front of the gate for three hours.
Tertiā hōrā ad portam vēnimus.
We came to the gate at the third hour.
Tribus hōrīs opus perfēcimus.
We finished the work within three hours.
These sentences use similar vocabulary but view time differently. The accusative lays out the action’s length; the ablative locates the event at a point or encloses its completion within a frame.
The full range of the contrasting ablative belongs on the ablative of time when and within which page.
Building the phrase
A cardinal number or quantitative adjective normally modifies a time noun in the accusative:
| Time unit | Duration phrase | Meaning |
|---|---|---|
| hōra, -ae | ūnam hōram; trēs hōrās | for one hour; for three hours |
| diēs, diēī | ūnum diem; decem diēs | for one day; for ten days |
| mēnsis, -is | duōs mēnsēs | for two months |
| annus, -ī | multōs annōs | for many years |
| nox, noctis | tōtam noctem | all night long |
| tempus, temporis | longum tempus | for a long time |
Tōtam noctem pluit, itaque viae lutulentae sunt.
It rained all night, so the roads are muddy.
Apud avunculum duōs mēnsēs manēbō.
I will stay with my uncle for two months.
Multōs annōs Rōmae habitāvit.
He lived in Rome for many years.
The duration phrase is adverbial: it measures the predicate rather than serving as the verb’s direct object. That is why trēs hōrās can accompany an intransitive verb such as maneō “remain” or dormiō “sleep.” Its accusative does not imply that anyone acts upon “three hours.”
No preposition is required
English speakers often add per because English has “for.” Bare accusative is the normal compact expression of simple duration.
Decem diēs in urbe mānsērunt.
They remained in the city for ten days.
Per + accusative is nevertheless valid when the speaker emphasizes the whole interval or uninterrupted continuation. It can be translated “throughout” or “for the whole of.”
Per tōtam noctem vigilāvimus.
We stayed awake throughout the entire night.
The difference is one of construal, not a ban: tōtam noctem simply measures duration, while per tōtam noctem presents the night as a stretch through which the activity continues. In many contexts the English translations overlap.
Duration with ordinal numbers
Latin can use an ordinal to locate a state in its currently running year, month, or day. Iam tertium annum rēgnat means “he has now been reigning into his third year” or “this is now the third year of his reign.” It does not mean a completed total of exactly three years.
Iam tertium annum hīc labōrat.
He is now working here for the third year running.
Aeger iam quīntum diem iacet.
The patient is now into his fifth day in bed.
This “current ordinal period” construction counts the incomplete period now underway: entering the third year means that two full years have elapsed and the third has begun. English often needs “for the third year,” “three years now,” or “going on three years,” depending on context.
Do not confuse it with tertiō annō, ablative, “in the third year.” The accusative measures the continuing span as counted; the ablative locates an event within that numbered year.
Borderline and alternative expressions
Classical authors occasionally use an ablative where duration is understood. In such passages the period is conceived as the temporal frame within which the action held, with full duration inferred. That variation is real, but it does not erase the basic opposition: use the accusative for an unmarked duration in composition and interpret an ablative from context.
Some nouns package duration lexically. Trīduum means “a period of three days,” so trīduum mānsit is itself an accusative extent. A journey can combine time and action: (formal narrative) cum trīduum iter fēcisset means “when he had marched for three days.”
Trīduum domī manēbō; deinde proficīscar.
I will stay at home for three days; then I will set out.
Expressions such as abhinc annōs trēs “three years ago,” post trēs annōs “after three years,” and ad vesperum “until evening” contain accusatives but are not all plain accusatives of duration. Their adverbs or prepositions contribute relations such as distance from now, sequence, or endpoint. Analyze the whole expression.
Register and use
The bare accusative of duration is productive in (informal) reconstructed conversation, (formal) prose, inscriptions, and (literary) verse. It is not an elevated idiom. Authors may front the duration for emphasis—tōtam noctem vigilāvit—or place it near the verb. Position does not change the case function.
Vague spans behave like numbered spans: breve tempus “for a short time,” longum tempus “for a long time,” and multōs annōs “for many years.” The phrase can measure an action, a state, a journey, or even an omission, provided the question is “how long?”
Common Mistakes
1. Using the ablative for ordinary duration
❌ Trēs hōrae exspectāvimus.
Incorrect—the duration is neither the subject nor a nominative phrase.
✅ Trēs hōrās exspectāvimus.
We waited for three hours.
2. Using the accusative for time when
❌ Tertiam hōram vēnit.
Incorrect for “he came at the third hour”; that asks when, not how long.
✅ Tertiā hōrā vēnit.
He came at the third hour.
3. Translating English “for” mechanically as per
❌ Prō duōbus annīs Rōmae habitāvī.
Incorrect—English “for” does not become prō; prō means “on behalf of” or “in place of” here.
✅ Duōs annōs Rōmae habitāvī.
I lived in Rome for two years.
4. Misreading an ordinal duration as completed cardinal time
❌ Iam trēs annōs rēgnat.
Wrong for the intended meaning “he is now in his third year”; this instead presents three years as a cardinal duration.
✅ Iam tertium annum rēgnat.
He is now in the third year of his reign.
Key Takeaways
Use the accusative to measure how long an action or state extends; use the ablative for when or within what time. Bare accusative is normal, while per emphasizes continuation through an interval. Cardinal numbers measure elapsed duration, whereas an ordinal accusative can count the period currently underway. The English preposition is not the rule—the temporal relation is.
Now practice Latin
Reading grammar gets you part of the way. The exercises are where it sticks — free, no signup needed.
Start learning Latin →Related Topics
- Accusative of Extent of SpaceA2 — Measure distance, length, width, height, and depth with the Latin accusative of spatial extent.
- Ablative of Time When and Within WhichB1 — Use the ablative to locate an event at a time or inside a deadline, and distinguish both from accusative duration.
- Case Functions without English PrepositionsB2 — Learn how bare Latin cases express relations that English usually marks with to, for, with, from, than, at, and other prepositions.
- Time ExpressionsA2 — Ask and say when something happens in Classical Latin using temporal adverbs, the ablative of time when, Roman hours, and conventional time phrases.
- Age and Duration ExpressionsA2 — Express completed age, a current year of life, elapsed duration, and time ago with the Classical Latin frames each meaning requires.