Answer: Of course!

When your most wanted date has already been passed, but in the calendar still is on "free", you are welcome to buy that day.

Your page will then be published, as soon as your payment has been registered and an administrator has checked the page's content. This page then is accessable at any time by the calendar or by typing in the date in the browser..

So this calendar-day will "always" be connected with YOUR special page!