Prepositions of time

In one line

à for clock time, en for months, years and seasons, dans for "in … from now", and no preposition at all for days of the week.

The table

Why some time words need a preposition and others do not

Take a completely ordinary sentence:

Je pars à huit heures et je reviens demain. I leave at eight and I come back tomorrow. /ʒə paʁ a ɥi.t‿œʁ e ʒə ʁə.vjɛ̃ də.mɛ̃/

One time expression took à, the other took nothing — in the same sentence. The difference is what kind of word it is, not what it means:

The test: can the word answer "when?" all by itself? demain can → it stands bare. huit heures cannot, it is only a number → it needs à.

English works the same way, which makes this one easy: at eight takes a preposition, tomorrow does not — and you would never say "at tomorrow".

And this à is the ordinary à, not a new rule: à Paris is a point in space, à huit heures is a point in time. One preposition, one meaning — see a-quatre-kar.

The trap: à demain is not wrong, it just means something else

❌ Je reviens à demain. — this blends the two and is wrong.

Four frequent errors

1. Days of the week take no preposition

English says "on Monday" and French says nothing at all:

Nor is there anything for months and dates that English marks: "in March" → en mars (a different word), "on the 15th" → le 15 (an article, not a preposition).

And the le shifts the meaning from "once" to "habitually":

Lundi, je travaille. — this coming Monday Le lundi, je travaille. — on Mondays

2. en versus dans

en is the time needed, dans is the wait before starting. Confusing these is one of the commonest errors there is.

English uses "in" for both — "I'll do it in an hour" is genuinely ambiguous in English and is usually resolved by context. French forces you to choose, so decide before you speak: how long it takes → en; when it starts → dans.

3. avant and après — with a noun and with a verb

avant de + infinitive, but après + past infinitive:

Avant de partir, j'ai mangé. — before leaving Après être parti, il a téléphoné. — after leaving

English uses "-ing" for both and gives you no warning — "before leaving", "after leaving". French uses two different structures, and the après one is the harder: it needs a compound infinitive, avoir mangé or être parti. The detail is in infinitif-passe.

4. pour — only for a planned future

pour is used when the period has not yet been lived through. For the past, use pendant.

English uses "for" in both, so this split has to be made deliberately.

Time expressions with no preposition

These take nothing at all and stand on their own:

❌ dans cette semaine ✅ cette semaine — as in English: "this week", not "in this week".

jusqu'à — and its contraction

Examples

Common mistakes

Why en covers both months and durations