I second this! An appointment calendar could be used for many purposes. In my case, I have a client that needs a site where users can schedule blocked time for sport vehicle rentals. They need to be able to select a time slot that is available and check out to pay for that time slot. Doing this manually has been a challenge. Having this feature would immediately make me sign up for a premium membership as it would save me lots of time and money. This feature would pay for the premium membership with the money I save. Please make this happen. Thank you!