Atlantic Standard Time (AST) is a time zone observed in several locations, including Halifax, Fredericton, and Charlottetown. It is four hours behind Coordinated Universal Time (UTC-4). This time zone is primarily used in the Atlantic provinces of Canada, specifically in Nova Scotia, New Brunswick, Prince Edward Island, and parts of Labrador in Newfoundland and Labrador. It is important to note that during daylight saving time, these locations may switch to Atlantic Daylight Time (ADT) which is UTC-3.