Custom Attributes on ActionResult

This is probably a rookie question but;

Let's say I have an ActionResult that I only want to grant access to after hours.

Let's also say that I want to decorate my ActionResult with a custom attribute.

So the code might look something like;

[AllowAccess(after="17:00:00", before="08:00:00")]
public ActionResult AfterHoursPage()
{
    //Do something not so interesting here;

    return View();
}

How exactly would I get this to work?

I've done some research on creating Custom Attributes but I think I'm missing the bit on how to consume them.

Please assume I know pretty much nothing about creating and using them though.