According to the United States Naval Observatory, there are a total of eight time zones in North America. They cover the land from Newfoundland in the far east to the Aleutian Islands of Alaska in the far west.
The time zones in America begin with time zone P*, which consists of the island of Newfoundland and is three and a half hours behind Greenwich Mean Time (GMT). The Atlantic time zone, covering the eastern part of Canada, is four hours behind GMT. Eastern, Central, Mountain and Pacific are the time zones in the continental United States. Most of Alaska lies in the Yukon time zone, and some of the Aleutian Islands fall in the Alaska-Hawaii time zone, which is 10 hours behind GMT.