Op maandag, om acht uur: saying when in Dutch

Use op with a day of the week or a date. English uses on here, so this one is easy.

Dutch · English

• Ik werk op maandag. · I work on Monday.
• Ik heb op vrijdag les. · I have a class on Friday.
• Mijn moeder komt op 3 mei. · My mother is coming on 3 May.

You can also leave out op: Ik werk maandag. That's correct too. Without op, people often mean this coming Monday. With op, it often means every Monday.

Days and months have no capital letter in Dutch: maandag, zondag, mei.

Use om with a clock time. English says at.

Dutch · English

• Ik begin om acht uur. · I start at eight o'clock.
• De les is om tien uur. · The class is at ten o'clock.
• Wij eten om half zeven. · We eat at half past six (6:30).

Careful with half: it points to the next hour. Om half negen = at 8:30, not at 9:30.

A day and a time together? First the day, then the time: Ik werk op maandag om negen uur. (I work on Monday at nine o'clock.)

More on clock times: Numbers and telling the time in Dutch.

Use in with a longer period: a month, a season or a year. Also with de week and het weekend.

Dutch · English

• Wij gaan in mei naar Spanje. · We're going to Spain in May.
• Ik fiets veel in de zomer. · I cycle a lot in summer.
• Mijn zus komt in 2027 naar Nederland. · My sister is coming to the Netherlands in 2027.
• Ik werk in de week, niet in het weekend. · I work during the week, not at the weekend.

In het weekend is a fixed phrase. English says at the weekend or on the weekend, but in the Netherlands you say in het weekend. (In Belgium you may also hear op het weekend.)

For a part of the day, you have two ways to say it. They mean the same.

With in · Without a preposition · English

• in de ochtend · 's ochtends · in the morning
• in de middag · 's middags · in the afternoon
• in de avond · 's avonds · in the evening
• in de nacht · 's nachts · at night

You hear the 's forms all the time. They have no preposition: 's is an old short form of des (of the), so it already does the job. Never say in 's avonds or op 's avonds.

Dutch · English

• Ik kook altijd 's avonds. · I always cook in the evening.
• Tom werkt in de middag en in de avond. · Tom works in the afternoon and in the evening.
• Eva werkt soms 's nachts. · Eva sometimes works at night.

A day and a part of the day? Make one word and use op:

• Ik heb op maandagavond les. · I have a class on Monday evening.
• Ik werk op zaterdagochtend. · I work on Saturday morning.

So: 's avonds on its own, but op maandagavond with a day.

With elke (every) you don't need op, om or in.

Dutch · English

• Ik werk elke dag. · I work every day.
• Ik bel mijn moeder elke week. · I call my mother every week.
• Ik kook elke maandag. · I cook every Monday.
• Ik werk elk weekend. · I work every weekend.

Weekend is a het-word, so elke becomes elk: elk weekend, elk jaar (every year).

So never op elke dag or in elke week.

Wrong · Right · Why

• ✗ Ik werk in maandag. · ✓ Ik werk op maandag. · A day takes op.
• ✗ Ik begin op acht uur. · ✓ Ik begin om acht uur. · A clock time takes om.
• ✗ om half negen = at 9:30 · ✓ om half negen = at 8:30 · Half points to the next hour.
• ✗ Ik werk om het weekend. · ✓ Ik werk in het weekend. · Om het weekend means every other weekend.
• ✗ Ik kook in 's avonds. · ✓ Ik kook 's avonds. · No preposition before 's.
• ✗ Ik werk op Maandag. · ✓ Ik werk op maandag. · Days have no capital letter.

• op + a day or a date: op maandag, op 3 mei, op maandagavond.
• om + a clock time: om acht uur, om half negen (8:30).
• in + a month, a season, a year, the week or the weekend: in mei, in de zomer, in 2026, in het weekend.
• 's ochtends, 's middags, 's avonds, 's nachts: no preposition. You can also say in de ochtend, in de avond.
• elke dag, elke week, elk weekend: no preposition.