I have yet another question that relates to the effectiveness of Tor.
Gmail (and therefore presumably other webmail operators) knows my computer's time zone. It does not know the time per se but the "time zone" as set (in Ubuntu) through clicking on the clock, selecting preferences, then choosing location.
Obviously this ignores the time (based on the location) of the Tor exit node.
I do not know how Gmail knows my computer's time zone, and, in which case, what other "local" information it can know.
Does anyone know how Gmail can do this and what other information from the client computer can be viewed. In other words, why can Gmail not, in theory, also view the real local IP?