am, um or im?

These three prepositions cover many common time expressions:

• um + clock time: um 9 Uhr
• am + day or time of day: am Montag, am Abend
• im + month or season: im Mai, im Winter

Years need no preposition at all: Ich bin 1990 geboren.

Practise these patterns alongside expressions such as morgen and in der Nacht.