Auto-set clock radios

I've had this clock radio for a long time. It's made by Timex, and it's auto-set. You just plug it in the wall and the correct time is displayed (off by a few minutes). It came with batteries, but you have to put them in yourself, yet they know the right time. Does anyone know how it works? Like some weird algorithm or something. Or is there just another battery on the inside? What if the clock was taken to a different time zone then, would it still know the correct time?

It has an internal battery, its clock was preset for the time zone it was sold in.

actually i remeber seeing a clock that set with some kind of satelite or something, maybe its that

Could it be a radio controlled clock? eg. Timex Radio Controlled Alarm Clock.

that's what i thought at first, until he said that it was off by a few minutes...

or it could be that clock is right and all the other clocks are wrong :-p