change calendar of wordpress plugin from days into days and hours

I've got a wordpress plugin for hotels and hotel owners, JS wordpress hotelsite [login to view URL]([login to view URL]). I want the calendar to be changed from days into days and hours. This is in frontend and backend. So now if you want a room, you need to fill in the date of checking in and date of checking out, I would like it to checkin on a date and an hour, and check out on a date and an hour. The total sum is for hours, so the visitors pays the room by the hour. and in the backend it works the same. The calender has a pop up. See also www.woonkamerwerkplek.nl.