I'd even hazard a guess to say that the ClientSide Technologies forum is a bit more appropriate, but the question is so broad that I'm not sure.
I guess a high level overview of what I think you're wanting to do might be: Store the interval end time in a server-side location (session, DB, etc.). On each page load, determine how long the client should way before performing the redirect, and generate the appropriate client-side output (Javascript, <meta> refresh tag, etc.) to accomplish the redirect.
An alternate method might be to use some AJAX on the client-side that periodically polls a script on your server to see if it's time to redirect yet.