In most cases, when I add a contact or company, they are in the same country and time zone as me. Many are in the same city as me - but the browser remembers those :-)
What could be cool is an input field that has a drop down selection of previously entered options to choose from. New entries would have to be checked against the country list ...
With the time zones - well - the option exists, so I have been adding it. Populating the timezone field and or contry/state combination would be nice :-)