Antarctica Standard Time is Greenwich Mean Time (GMT).
Bases and stations around Antarctica tend to keep either the time relating to their home territory. Examples:
GMT = Greenwich Mean Time; NZST = New Zealand Standard Time; NZDT = New Zealand Daylight Time; SAST = South Africa Standard Time; CLT = Chile Time; CLST = Chile Summer Time;
In Antarctica, the U.S. stations uses New Zealand time because most Americans who go to Antarctica for the U.S. Antarctic Program fly to and from there via Christchurch.