No, I did not cheat here. When the jam started there was the button to submit your game and there you could choose between uploading an existing game or creating a new one. Somehow that date got saved for my submission when I finally released my game. I know that it is really confusing. It is also bugging me, but I didn't want to change something because I noticed it after the deadline was over. But I can assure you, that I made this game during the jam. So please rate the game. If you want evidence, I can show you my Bitbucket commits of the project ;)