Hide the important bits of code inside tons of useless other code. Make use of the eval(String.fromCharCode(<ascii values of your code here>)) function for both important and unimportant bits of the code to further obscure the whole thing. (Want to hide a tree? Place it in a forest!)
There is a choice of "code uglifiers" out there. Google will find them for you. Run your code through one of them and be prepared for a surprise when trying to read your own code.
Do the actual relocation on the server side using header("Location: <url>"). Your client side code has to set a cookie to get the client's timezone to your server, or just place the current client's time in the cookie and calculate the timezone yourself on the server side. Even if someone's really, really curious and gets down to the important bits, placing the current time in a cookie is nothing much suspicious, as has been said before.
Have your "grab the time(zone)"-function do something really nice for the user at the same time, which might satisfy the user's curiosity and stop him from looking any further.
I see one drawback though: When I run into some code which literally cries "Don't ever understand me!" this fact alone is a real challenge for me to have a much closer look at it. Well, that's me of course...
I really shouldn't have written all this...