German Time Expressions: Which Case, Which Preposition

Most learners meet German time phrases one at a time, as vocabulary: am Montag, jeden Tag, seit einem Jahr, vor zwei Wochen. Nobody ever tells them there is a system underneath, so they end up guessing at *in Montag, *seit ein Jahr, *jede Tag. The system is small enough to fit on one page. A time phrase with no preposition is almost always accusative. A time phrase with a preposition is almost always dative. The genitive shows up in a handful of fixed phrases you should recognise and never build yourself.

That rule of thumb covers roughly 90% of what you will say or hear. The remaining 10% is the short list of prepositions that behave differently from their English translations - in meaning "from now", vor meaning "ago", seit demanding present tense - and those are worth ten minutes of deliberate attention. If you need the clock itself (halb acht, Viertel nach, the 24-hour system), that is a separate skill; see numbers and time.

The core split: no preposition means accusative

German marks time on the noun phrase when there is no preposition to do the job. This is the adverbial accusative, and it does two things: it points at a specific time, or it measures a span.

• Pointing: nächsten Montag, letztes Jahr, diesen Sommer, jeden Tag, den ganzen Abend
• Measuring: Ich habe drei Jahre in Wien gewohnt. Wir haben zwei Stunden gewartet.

Feminine and plural forms hide the case (nächste Woche looks identical in nominative and accusative), which is exactly why learners never notice the pattern. The masculine gives it away: it is nächsten Monat, letzten Freitag, jeden Tag - never *nächster Monat. If you can get the masculine endings right, the rest follows automatically. The library has the full accusative endings table if the article forms are still shaky.

The moment a preposition appears, that preposition assigns the case, and the temporal prepositions are overwhelmingly dative: an, in, vor, nach, seit, ab, von ... bis, zu, bei, zwischen. The accusative ones are a short list: um, gegen, für, bis, über, durch.

Wann? Points in time

This is the table people actually need. Note that an dem contracts to am, in dem to im, zu dem to zum, bei dem to beim - the contraction is standard, not casual.

Two things to burn in. First, am is for days and daytimes, im for months and seasons, um for clock times, and nothing at all for a bare year. *In 2019 bin ich umgezogen is an anglicism that native speakers do notice; say 2019 bin ich umgezogen or im Jahr 2019. Second, the night is the odd one out: am Morgen, am Abend, but in der Nacht.

The -s adverbs

montags, abends, morgens, sonntagabends - lowercase, no article, no case at all - mean habitually. Am Montag arbeite ich nicht is about one specific Monday; Montags arbeite ich nicht is about every Monday. This distinction is invisible in English ("I don't work Mondays") and it does real work in German. morgen früh means tomorrow morning; heute Morgen means this morning, already past. There is no *morgen Morgen.

Wie lange? Duration, and the seit trap

Duration is where the biggest interference from English happens, because English uses "for" everywhere and German splits the job four ways.

The seit rule is the single highest-value item on this page. German uses the present tense where English uses the present perfect: Ich lerne seit zwei Jahren Deutsch = "I have been learning German for two years." Using the perfect (*Ich habe seit zwei Jahren Deutsch gelernt) makes it sound finished. And seit is dative, so it is seit einem Jahr, seit einer Woche, seit zwei Jahren - watch the -n on plural datives.

On für + accusative for duration: you will hear Ich war für drei Jahre in Berlin from younger speakers, and it is spreading under English influence. It is still marked. The safe, unmarked version for a completed stretch is the bare accusative: Ich war drei Jahre in Berlin. Keep für for a stay you are planning: Ich fliege für zwei Wochen nach Spanien.

Wie oft? Frequency

Frequency is nearly all accusative, and nearly all invisible once you know that.

• jeden Tag, jede Woche, jeden Monat, jedes Jahr - accusative, and the masculine -en is the one people drop
• alle zwei Tage, alle drei Wochen - "every other day", "every three weeks"
• einmal die Woche (accusative) or einmal in der Woche (dative) or einmal pro Woche - all three are correct and interchangeable
• dreimal am Tag, zweimal im Monat - dative with the preposition
• montags, wochentags, täglich, wöchentlich, monatlich - adverbs, no case

Note that jeden Tag and täglich are not stylistically identical: täglich is what appears on medication instructions and contracts, jeden Tag is what you say to a friend. These pairings live in collocations rather than in a grammar table.

The four that trip everyone up

`in einer Woche` = a week from now, not "for a week". Ich bin in einer Woche fertig means you will be finished next week, not that finishing will take a week. For that, use the bare accusative: Das dauert eine Woche.

`vor einer Woche` = a week ago. vor normally means "in front of" or "before", but followed by a bare span of time it is the standard word for "ago", and it is dative: vor einem Monat, vor drei Tagen. There is no separate word for "ago" in German.

`nach` vs `in` for future distance. nach zwei Wochen means "after a two-week period had passed", usually inside a narrative about the past: Nach zwei Wochen ist er zurückgekommen. For "in two weeks" from now, it is in zwei Wochen.

`bis` is accusative and often bare. bis nächsten Montag, bis Ende Juli, bis morgen. When an article is needed it stays accusative: bis den 3. Mai, though bis zum 3. Mai with dative zu is more common and safer.

The genitive: recognise, do not build

German has a genitive of indefinite time, and it is almost entirely fossilised: eines Tages (one day, some day), eines Abends, eines Morgens, and by analogy the grammatically irregular eines Nachts - Nacht is feminine, but the phrase copies the masculine ending anyway. There is no productive pattern to extend here. You cannot invent *einer Woche to mean "one week".

The genitive prepositions do stay alive in written German: während des Krieges, innerhalb einer Woche, außerhalb der Öffnungszeiten, Anfang des Monats, Ende der Woche. In speech, während frequently takes dative, and nobody minds. And Anfang, Mitte, Ende drop the article entirely before a month: Anfang Juli, Mitte September, Ende März.

Honest advice: at A2 and B1 this is recognition vocabulary. Learn to read eines Tages without stumbling and move on. If you want exhaustive lists of every temporal preposition with every register variant, a reference grammar - Hammer's German Grammar and Usage is the standard - will serve you better than any app, ours included. What an app is good for is making the fifteen high-frequency patterns automatic, which is a different job.

Make them automatic, not memorised

Time phrases are the perfect thing to drill in spaced repetition, because they are short, they are chunked, and you need them retrievable in under a second while you are speaking. Nobody has time to reason "seit is dative, Jahr is neuter, so einem" mid-sentence. You need seit einem Jahr to come out whole.

On merke.me, the time-expression material sits across three layers: the case system in library, the individual words like wöchentlich and damals in vocab, and the fixed chunks - vor einer Woche, Anfang Juli, alle zwei Tage - in collocations, scheduled so they come back exactly when you are about to forget them. Browse the decks to see how the A1-C2 sequence introduces them, or check pricing if you have already decided. Then take the four trip-ups above and write one true sentence about your own week with each of them - that single exercise catches more errors than another read of the table.