At the Pole, every time zone meets
At the geographic South Pole, the usual link between time and location breaks down. Time zones are defined by longitude, but every line of longitude converges at the pole. Step a short distance in any direction and you are heading north; there is no east or west to give the place a unique local time.
So the station there has to pick a clock by convention. It uses New Zealand time—not because New Zealand is nearby on the map, but because that is the practical choice for running the base.
The supply route sets the clock
The Amundsen–Scott South Pole Station is supplied and supported through New Zealand, with flights operating via Christchurch. Keeping station clocks aligned with that logistical hub makes schedules easier to coordinate: crews, aircraft, communications, and daily operations can all work from the same time standard.
In other words, the clock follows the human network that connects the station to the outside world, rather than the Sun’s position overhead. The Pole’s long periods of continuous daylight and darkness make ordinary sunrise-and-sunset cues especially unhelpful for keeping a daily schedule.
A choice, not a natural answer
There is no special “South Pole time” dictated by geography. The station could, in principle, use another time zone; New Zealand time is the useful convention for its operations. That means a traveler standing at the exact point where all longitudes meet can check the clock and get a clear answer—but only because people have agreed which clock to follow.
