Kind of confusing, isn’t it?
Antarctica sits on every line of longitude, due to the South Pole being situated near the middle of the continent. Theoretically Antarctica would be located in all time zones, however areas south of the Antarctic Circle experience extreme day-night cycles near the times of the June and December solstices, making it difficult to determine which time zone would be appropriate. For practical purposes time zones are usually based on territorial claims, however many stations use the time of the country they are owned by or the time zone of their supply base. [Source: Wikipedia]