Days of the Week with 'op'
To talk about things happening on a specific day of the week, Dutch uses the preposition op. This is the direct equivalent of the English "on" (as in "on Monday").
Notice that unlike in English, days of the week in Dutch (maandag, dinsdag, woensdag, donderdag, vrijdag, zaterdag, zondag) are written with lowercase letters unless they start the sentence.
You can easily combine op with exact times (using om).
Starting with the Day (Word Order)
If you want to emphasize when something happens, you can move the day to the very beginning of the sentence.
When you do this, you must apply the primary rule of Dutch sentence structure: the verb is always the second element. If your sentence starts with an "Op [day]" phrase, the verb must come immediately next, swapping places with the subject.
Asking Questions
When asking a yes/no question, the verb moves to the front of the sentence, followed by the subject, and then your time phrase with op.