You can remove yourself from a tee-time as long as you're a day ahead of the booking (24hrs in advance minimum) and as long as it's not paid. To do so:
Log in your profile on www.chronogolf.com and click on ‘’view or modify’’ next to your tee-time.
There's an 'X' next to your name, when you click that a window will pop up to confirm you want to remove yourself.
Follow the steps as seen in the screenshots below: