Christchurch is the logistics hub and support base for the US presence in Antarctica, so I believe all US facilities on the continent conduct their work in that time zone.
Well, not Palmer, since that's supported by a research vessel from Chile.
It's also amusing because the tourist camp less than a km from Amundsen-Scott also goes by Chilean time. The tourist camp staff invited us over for Christmas when I was down at Pole, but it was like 3 am for them...
'The station uses New Zealand time (UTC+12 during standard time and UTC+13 during daylight saving time) since all flights to McMurdo station depart from Christchurch and, therefore, all official travel from the pole goes through New Zealand.'
