Dutch uses different prepositions depending on the type of time reference. Om is used for clock times: om drie uur, om half acht. Op is used for days and specific dates: op maandag, op 15 april, op mijn verjaardag. In is used for months, seasons and years: in januari, in de zomer, in 2024. These three cover the bulk of everyday time expressions and are worth prioritising first when studying Dutch prepositions.
Voor (before), na (after), tijdens (during), vanaf (from), tot (until) and tegen (around or towards) fill in the temporal picture. Tegen is particularly useful for approximations: tegen de avond (towards evening), tegen het weekend (around the weekend). Binnen means within a time period: binnen een uur (within an hour). Geleden meaning ago follows the time expression: drie jaar geleden. Over meaning in for a future event precedes the time period: over twee weken (in two weeks).
A few expressions require no preposition where English uses one: morgen, gisteren, vorig jaar, volgende week. And the definite article sometimes replaces a preposition in set phrases: de hele dag (all day), het hele jaar (all year). Building a personal list of time expressions with their correct prepositions and reviewing it regularly is the most efficient path to internalising these patterns for productive use.