Learn Dutch: De afspraak is op de zesde september. - The appointment is on the sixth of September.

Dutch doesn't use a preposition like "of" for dates. You simply put the ordinal number (like zesde) directly before the month, just like saying "the sixth September".

Why is september written with a lowercase letter?

In Dutch, months, days of the week, and seasons are never capitalized unless they are the very first word of a sentence. So it is september, not September.

How do you form the word zesde (sixth)?

To make an ordinal number (like first, second, third) in Dutch, you usually add -de or -ste to the base number. For zes (six), you add -de to make zesde. Numbers from 1 to 19 generally get -de, except for a few irregular ones like 1st (eerste) and 8th (achtste).

Could I just say "op zes september" instead of using de zesde?

Yes, and in fact, using the normal number (zes) without de is much more common in everyday Dutch. You will hear op zes september more often than op de zesde september.

Does afspraak only mean "appointment"?