Both are correct, and there isn’t much difference between them. I personally feel like though if you say “when does (something) start?” it usually means you already know it will start soon, just don’t know exactly when. “When will (something) start?” usually is more general and could even apply to something you have no idea when it starts. BUT, to be honest they’re pretty much interchangeable and there’s little to no difference in them.

Hi Aleksandr, These are extremely similar and both can be used. If any difference I would say using ‘when will the meeting start’ would suggest the person is asking about a meeting later on that day and ‘when does the meeting start’ could possibly mean it is about to start or should have maybe started already. Thanks Adam