Yes, your game will be fine.
If you want to transfer them over and trade them, and want to be on the safe side, it wouldn't hurt until after that day passes once you set your date and time back. (Though it shouldn't hurt if you didn't)
I used to do this all the time, and have even put my date back to before I started my game, and nothing happened, so I'm fairly confident nothing will happen to you. Also, congrats on the shiny!