It's always hard to guess all the reasons why someone would want a different page everyday of the month and I don't know more about the project than what is written above. Considering this, maybe there are just parts of the page that are changing everyday and you could load them on the server-side thus having a single page loading including other pages depending on the day. The problem is that you would have to ask the timezone of the user and keep it in a cookie.
var dayOfTheMonth = (new Date()).getDate(); location.href="page" + dayOfTheMonth.toString() + ".html";
This is the way I would do it, do you have any other suggestions?