This is probably the hardest part about selling a game. It is important to have a press release that includes a release date, but what you don’t want is to have a game that gets delayed past your original release date. In order to avoid this, make your release date vague. Saying TBD-To Be Determined or TBA-To Be Announced is perfectly fine! You can also say Q1/2/3/4 and the year. Never announce your internal release date to the public until you are 110% sure you can follow through on it!
Here’s a thought: why not finish the game first, announce the release date, create a ton of hype for the game, and then release it! This way allows you to focus in on the development side and then on the marketing side. Hopefully you’ll be good at both! 😉