display users local time

Greets all - I seem to be missing something obvious. I want to display the date/time according to the users local settings. Best as I can see I need to know two vars to do this, the local users LANG and the TZ they are in. Does the browser pass this info in the header somewhere were php can read it? I don't want to hard code in to display the time / date in any one region. Once I know the LANG and the TZ I know I can use the setlocale(), strftime(), and other date / time functions to manuplate the date / time in to what I want. I'm just missing where to get the users local settings from... Thanks for any help. -- Scott