The world is divided into 24 time zones. One of the zones belong to Greenwich Mean Time (GMT) which during the winter it is the same time zone as London. The special about this time zone is that it doesn't have Daylight Saving Time (DST) and it doesn't change throughout the year. In order to avoid confusion pilots normally speak with ATC (Air Traffic Control) in GMT rather than the local time wherever they go.
A pilot landing in New York and comes from Nevada, will speak with ATC in GMT. It doesn't matter where he comes from or if in his origin airport has DST or not. This is how pilots and ATC all over the world can talk to each other in a common language. At Torgoen we offer a range of watches with a second time zone hand that displays a second time zone in a 24 hour format (or military time). One can set that hand to any time zone of one's choice.
