Build a planning avalabilities

Hi, I want to build a planning availabilities per users. I already have an idea but I don't know if it is the easiest one to implement. I already have a user model. I could create a unavailabilites table with these columns: id, from, to, user_id

And I have a calendar view where i check for each hours of the day the unavailabilities. And then I am able to build the unavailabilities table.

What do you think? Greg