The pattern
Inside a sentence, days and months are lowercase. Use op before a day or a date: op vrijdag, op 3 april.
- Days: maandag, dinsdag, woensdag, donderdag, vrijdag, zaterdag, zondag.
- Months: januari, februari, maart, april, mei, juni, juli, augustus, september, oktober, november, december.
- A month or a year on its own takes in: in mei, in 2025. More in Om, op, in: talking about time.
- For the coming day, people often drop op: Ik bel je dinsdag.
- A date is number plus month: 3 april, said drie april. Formal speech sometimes uses an ordinal (a number that shows order, like third): de derde april.
- Years before 2000 are said in hundreds: negentienhonderdnegentig. From 2000 on, the usual form is tweeduizend vierentwintig. For recent years you also hear twintig vierentwintig.
Examples
| Sanne gaat op zaterdag naar de markt. | Sanne goes to the market on Saturday. |
| Is de supermarkt op zondag open? | Is the supermarket open on Sunday? |
| Daan is op 14 mei jarig. | It's Daan's birthday on 14 May. |
| Het is vandaag dinsdag 3 maart. | Today is Tuesday 3 March. |
| Ik heb op vrijdag 6 juni een afspraak bij de huisarts. | I have a GP appointment on Friday 6 June. |
| Yara heeft in augustus vakantie. | Yara has time off in August. |
| De burgemeester opent de nieuwe bibliotheek op de derde april. | The mayor is opening the new library on the third of April. |
| Fatima is geboren in negentienhonderdnegentig. | Fatima was born in 1990. |
| Lotte werkt hier sinds twintig tweeëntwintig. | Lotte has worked here since 2022. |
Why it works this way
Picture a wall calendar. A day or a date is one square, and you put your finger op it. A month is a whole page and a year is the whole calendar: you are in them. English works almost the same way (on Monday, in May), so you can mostly trust your instinct.
Remember: one square takes op, a whole page takes in.
As for the small letters: Dutch treats maandag and mei as ordinary nouns, like fiets or brood. They get a capital at the start of a sentence, like any word, and in holiday names such as Goede Vrijdag. See Capital letters.
Dates run from small to big: day, month, year. Dutch people write dates in figures the same way, so 3-4-2026 on a letter from the gemeente means 3 April, not 4 March.
Years work like English nineteen ninety, except that Dutch keeps the word honderd and writes it all as one word. In everyday writing you just use figures: in 1990. For building the numbers themselves, see Numbers.
Watch out
错误Ik werk op Maandag thuis.
正确Ik werk op maandag thuis.
days are lowercase, unlike in English and German
错误De afspraak is op mei 12.
正确De afspraak is op 12 mei.
the number comes before the month
错误Ik ben op juni jarig.
正确Ik ben in juni jarig.
a month on its own takes in
错误Mijn verjaardag is in 5 mei.
正确Mijn verjaardag is op 5 mei.
a date takes op, just like a day
Quick check
- Choose op or in: Ik ga ... juli op vakantie.
- Choose op or in: Is de bibliotheek ... zaterdag open?
- Fix the two mistakes: Mijn verjaardag is op Mei 4.
- Write 1985 in words, the way people usually say it: Sanne is geboren in ...
显示答案
- in: a month on its own takes in.
- op: a day takes op.
- Mijn verjaardag is op 4 mei. The month is lowercase and the number comes first.
- negentienhonderdvijfentachtig: years before 2000 are said in hundreds, as one word.
Use it today
Open your calendar and say three plans for this week out loud, with the day and the date, like Op donderdag 15 oktober ga ik naar de tandarts. Then ask a colleague: Wanneer ben jij jarig?