#1). First of all, the 220 volts has to be changed to something near 110 volts. The most convenient way to do that is with a 2:1 step-down transformer. Those are readily available, for exactly this purpose, in kits of "travelers' accessories".
#2). Since Steve's immediate concern is his alarm clock, there's another important detail that he needs to consider. The power from the electrical outlets in the US is supplied at 60Hz, whereas the power in most of the rest of the world comes out at 50Hz. Many clocks use the frequency of the power outlet to keep time. If his 110V alarm clock is one of those and is designed for 60Hz, then if it's run on 50Hz power, it'll lose 10minutes of time every hour !
Steve's easiest and most economical solution might simply be to buy an alarm clock when he lands in New Zealand.
