This WordPress plugin helps customer to select available time slot for a certain date.
Then the sold out time slots become not available for that date.

You can use any text titles for the time slots not only the hours.
Ability to specify price per slot.
Ability to specify maximum number of orders per slot.
You can disable holidays.
The same calendar can be used for multiple products.
All ordered time slots can be viewed on edit product page in the WordPress dashboard.
Selected time slots by customer are saved in text field product custom option. So they are visible on order info page and in order confirmation emails.

Installation instructions:
README.html

Modifications:
http://hottons.com/ocl_modifications


Frontend:
http://hottons.com/demo/wp/ocl/product/test-product/

Try FREE Date Price Calendar plugin:
https://wordpress.org/plugins/date-price-calendar/


If you cannot use or don't like this plugin you can get a refund.