Learn Dutch: Wanneer ga je jouw verjaardag vieren? - When are you going to celebrate your birthday?

This sentence uses the future tense with the verb gaan (to go). In Dutch, when you use a helper verb like gaan, the main action verb (vieren, meaning to celebrate) gets pushed to the very end of the clause in its full dictionary form (the infinitive).

Why is it ga je and not gaat je? Doesn't the 'you' form usually end in -t?

You are right that the standard form is je gaat. However, this is a question starting with a question word (Wanneer), which causes the verb and subject to swap places. A special rule in Dutch is that when je or jij comes directly after the verb, the verb drops its -t. So it becomes ga je.

Why does the sentence use jouw for 'your' instead of just je?

You can absolutely say je verjaardag. But because the sentence already uses je right before it as the subject for 'you' (ga je), saying ga je je verjaardag sounds a bit clunky. Using jouw avoids repeating the exact same word twice in a row and sounds much more natural.

How exactly does gaan create the future tense here?