am, im or um?
a1Three prepositions for three sizes of time: am for days and parts of the day, im for months and seasons, um for a clock time.
am
Days of the week, dates and parts of the day: am Montag, am 3. Mai, am Morgen, am Wochenende. Short for „an dem“. One exception: in der Nacht.
Am Freitag habe ich frei.I'm off on Friday.
im
Months and seasons: im Januar, im Sommer, im Winter. Short for „in dem“.
Im August fahren wir nach Italien.In August we're going to Italy.
um
A clock time, always without an article: um acht, um halb neun, um Mitternacht.
Der Zug fährt um sieben Uhr.The train leaves at seven.
The mistake
Wir treffen uns in Montag.
Wir treffen uns am Montag.
Days of the week always take „am“. „im“ belongs to months and seasons, that is, to longer stretches of time.
Rule of thumb
Smallest unit to largest: clock time um, day am, month im. Years and repeated weekdays take no preposition at all: 2026, montags.
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