Esperanto uses the same measurement logic for time that it uses for length, weight, and price. A bare expression answering kiom longe? “how long?” or kiel ofte? “how often?” commonly takes accusative -n: Mi atendis du horojn. Frequency can also be packaged with fojo, -foje, or an adverbial time unit such as tage “per day/daily.”
Duration with the measured accusative
A time phrase that measures the extent of an event normally takes -n when it has no preposition:
Ni atendis kvardek minutojn, sed la buso ne venis.
We waited forty minutes, but the bus did not come.
La festivalo daŭros tri tagojn kaj du noktojn.
The festival will last three days and two nights.
The time phrase is not necessarily the verb's direct object. Kvardek minutojn measures the extent of atendis; nobody is “waiting the minutes.” Esperanto uses -n for this adverbial measurement because it marks a role that could also be expressed with a preposition.
Only the count nouns and their adjectives change form. Cardinal particles remain invariant:
Mi laboris du longajn horojn sen paŭzo.
I worked for two long hours without a break.
Du has no ending; longajn horojn has plural -j and measured -n. For a detailed account of this non-object use, see the accusative of time duration.
Duration with dum
Dum can introduce the same duration explicitly. A preposition already marks the phrase's role, so the noun after dum does not receive accusative -n:
Ni atendis dum kvardek minutoj, sed la buso ne venis.
We waited for forty minutes, but the bus did not come.
Ŝi loĝis en Kioto dum ses monatoj.
She lived in Kyoto for six months.
The bare measured form and the dum form are usually equivalent when an exact duration is given:
La matena kunveno daŭris du horojn.
The morning meeting lasted two hours.
La matena kunveno daŭris dum du horoj.
The morning meeting lasted for two hours.
The first is compact and very common; the second makes the interval explicit. Dum also introduces a period identified by an event rather than measured numerically: dum la kunveno, dum la somero, dum mi dormis. In that use, simply removing dum is not possible.
Do not add -n after dum merely because English says “for.” Ordinary prepositions block this measured accusative.
When the time quantity is the subject
A time expression does not automatically take -n. If it is the subject or a predicate complement, it stays nominative:
Tri horoj pasis antaŭ ol iu respondis.
Three hours passed before anyone answered.
Dek minutoj estas tro mallonga tempo por tiu prezento.
Ten minutes is too short a time for that presentation.
Compare Ni atendis tri horojn with Tri horoj pasis. The quantity is identical, but its syntactic job differs. Esperanto marks the job, not the meaning “time” by itself.
Counting occasions with fojo and -foje
Fojo means an occasion. As an ordinary noun it takes plural and measured accusative endings:
Mi telefonis al la kliniko tri fojojn hodiaŭ.
I called the clinic three times today.
The compact adverbial compound trifoje expresses the same occasion count:
Mi trifoje kontrolis la adreson antaŭ ol sendi la pakaĵon.
I checked the address three times before sending the package.
Both are neutral in speech and writing. The separate form highlights the count; the compound packages it as a manner/frequency adverb. Unufoje means “once,” whereas unue means “first/firstly” in an ordering:
Unue legu la instrukciojn; poste premu la butonon unufoje.
First read the instructions; then press the button once.
Do not confuse occurrence count with multiplication. Dufoje means “on two occasions”; duoble means “by a factor of two.” The contrast is developed on multipliers and repetitions.
Frequency per time unit
Esperanto often forms an adverb from the unit: tage “per day/daily,” semajne, monate, jare. Combine it with an occasion count:
La trajno al la marbordo veturas kvarfoje tage.
The train to the coast runs four times a day.
Mi naĝas du fojojn semajne kaj promenas ĉiutage.
I swim twice a week and walk every day.
The -e form supplies a recurring frame, not a duration. Mi laboris semajne is incomplete or context-dependent if you mean how many hours per week; state the rate: Mi laboris tridek horojn semajne.
Ĉu vi ankoraŭ laboras kvardek horojn semajne?
Do you still work forty hours a week?
Here kvardek horojn is the measured amount of work, while semajne gives the unit over which that amount recurs.
Other transparent forms include ĉiutage, ĉiusemajne, and ĉiumonate. Ĉiu plus an accusative time noun is equally normal:
La teamo kunvenas ĉiun merkredon je la naŭa.
The team meets every Wednesday at nine.
Ĉiun merkredon is a recurring time-point adjunct, not measured duration. The same -n form can therefore answer either “for how long?” or “when/how often?”; context supplies the interpretation.
Intervals: every second day and every few hours
An ordinal specifies the spacing in a recurring series:
La kolektado okazas ĉiun duan sabaton.
The collection takes place every other Saturday.
Dum la vojaĝo ni haltis ĉiun trian horon por ripozi.
During the journey we stopped every three hours to rest.
In ĉiun duan sabaton, the event occurs on alternate Saturdays. Dusemajne can be ambiguous internationally between “every two weeks” and “twice a week,” because national-language habits influence interpretation. For clarity, say ĉiun duan semajnon for every two weeks and du fojojn semajne for twice a week.
Distribution with po
Po marks the quantity assigned to each repeated occasion, person, or unit. It stands immediately before that distributed quantity:
La kuracisto diris, ke mi prenu po du tablojdojn tri fojojn tage.
The doctor said I should take two tablets at a time, three times a day.
The sentence contains two separate numerical relations. Po du tablojdojn distributes two tablets to each occasion; tri fojojn tage counts the occasions per day. Placing po before the time unit would change what is distributed.
Start, end, and total span
Use de … ĝis … to name the endpoints of a period and dum or a measured accusative to state its total length:
La oficejo estas malfermita de la oka ĝis la kvina, entute naŭ horojn.
The office is open from eight until five, nine hours in total.
Ekde emphasizes a starting point from which a state continues: Mi laboras ĉi tie ekde Januaro. Dum Januaro instead locates something within the month or says it lasted through that month. These are time relations, not alternative ways to form a cardinal.
Fractional durations follow ordinary number grammar. Duona horo is a half hour; in a measured phrase use duonan horon. A mixed duration is often clearest when coordinated:
La filmo daŭras unu horon kaj duonon.
The film lasts one and a half hours.
In numeric schedules, 1 h 30 min is compact (technical) notation. In learner-facing prose, words usually prevent ambiguity.
A short exchange
— Kiom longe daŭras la kurso? — Dek du semajnojn, kun du lecionoj semajne.
— How long does the course last? — Twelve weeks, with two lessons per week.
The answer separates duration (dek du semajnojn) from frequency (du lecionoj semajne). English often leaves both relations to the preposition “for” or the phrase “a week”; Esperanto makes their grammatical roles visible.
Common Mistakes
Leaving a bare duration nominative
❌ Mi atendis du horoj ĉe la stacio.
Incorrect — a bare measured duration takes accusative -n.
✅ Mi atendis du horojn ĉe la stacio.
I waited two hours at the station.
Adding accusative after dum
❌ Mi atendis dum du horojn.
Incorrect — dum already marks the time phrase's role.
✅ Mi atendis dum du horoj.
I waited for two hours.
Pluralizing the cardinal
❌ Mi ekzercas duj fojojn semajne.
Incorrect — cardinal du never takes plural -j here.
✅ Mi ekzercas du fojojn semajne.
I exercise twice a week.
Confusing “once” with “first”
❌ Premu la butonon unue.
Wrong if the instruction means one press; unue means first.
✅ Premu la butonon unufoje.
Press the button once.
Using an ambiguous compact interval
❌ La bulteno aperas dusemajne.
Avoid this when exact frequency matters; readers may infer two different schedules.
✅ La bulteno aperas ĉiun duan semajnon.
The bulletin appears every two weeks.
Key Takeaways
Use a bare accusative phrase for measured duration, or dum plus a nominative-form phrase when the interval is explicitly introduced. Count occasions with fojo/foje, state a recurring rate with tage, semajne, monate, and use ĉiu + ordinal + time noun for regular spacing. Keep cardinal particles invariant and distinguish the measured amount, the recurring unit, and any quantity distributed with po.
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Start learning Esperanto →Related Topics
- Time DurationA1 — Express how long an event lasts by marking a time measure with -n or by using an explicit duration phrase.
- Multipliers and RepetitionsA2 — Distinguish multiplication with -obl- from repeated occasions with fojo, and form each pattern productively.
- Cardinal NumbersA1 — Use Esperanto cardinal numbers to count, quantify noun phrases, identify items, and read basic dates, times, measurements, and decimal notation.
- DumA2 — Use dum before a time expression or clause to place one event within the duration of another.
- Time and Frequency ExpressionsB1 — Use Esperanto's productive frames for clock time, recurring events, duration, and temporal sequence without importing English prepositions.
- AgeA2 — Ask, state, compare, and describe age in Esperanto with aĝi, -jara compounds, measurement case, and formal age phrases.