How to use the prepositions in and an

When do we use the German prepositions: "in" and "an"?

The prepositions "in" and "an" are two-way prepositions and we can use them in the accusative and in the dative case. So I have to ask “wo” or “wohin”? But with the question “when”? I always have to ask for a temporal position, that means "in" and "an" are here temporally always in the dative.

The assignment of the correct preposition is semantic:

"In": seasons

In + article dem - im Frühling (im Frühling, im Sommer, im Herbst und im Winter)

- In + article dem - im "im Frühling", " im Sommer", etc.

"In":Months

- In + article dem - im "im Januar", "im Februar", etc.(Januar, Februar, März, April, Mai, etc.)

"An": days of the week

- am “am Montag", “am Dienstag", etc. (Montag, Dienstag, etc.)

“An” - Times of day (am Morgen, am Vormittag, am Abend… ).

An + article dem: am Morgen "in the morning", “in the evening", etc.

BUT

In der Nacht because the noun night is feminine.