In Canada, the provinces of New Brunswick and Nova Scotia reckon time specifically as an offset of 4 hours from Greenwich Mean time (GMT-4). (UTC is regularly adjusted by means of leap seconds to keep it synchronized to with within 1 second of GMT.) Prince Edward Island and small portions of Quebec (eastern Côte-Nord and the Magdalen Islands) are also part of the Atlantic Standard Time Zone. Officially, the entirety of Newfoundland and Labrador observes Newfoundland Standard Time, but in practise Labrador uses the Atlantic Standard Time Zone.

Other parts of the world that keep time by subtracting four hours from UTC include Bermuda, in the North Atlantic; many Caribbean islands, including Puerto Rico, the US Virgin Islands; and several South American countries, such as Paraguay, Chile, Bolivia, and parts of Brazil. Venezuela used AST until December 9, 2007, when it switched to .

AST is known (where applicable) as Atlantic Daylight Time (ADT) during daylight saving time, and has one hour added to make it three hours behind GMT (UTC-3).

Major metropolitan areas

• Asunción, Paraguay
• Bridgetown, Barbados
• Cape Breton Regional Municipality, Nova Scotia
• Charlotte Amalie, U.S. Virgin Islands
• Charlottetown, Prince Edward Island
• Concepción, Chile
• Fredericton, New Brunswick
• Georgetown, Guyana
• Halifax, Nova Scotia
• Hamilton, Bermuda
• La Paz, Bolivia
• Manaus, Brazil
• Moncton, New Brunswick
• Oranjestad, Aruba
• Port of Spain, Trinidad and Tobago
• Saint John, New Brunswick
• San Juan, Puerto Rico (no DST)
• Santa Cruz, Bolivia
• Santiago, Chile
• Santo Domingo, Dominican Republic
• Sucre, Bolivia
• Summerside, Prince Edward Island
• Willemstad, Netherlands Antilles

Sources

• World time zone map
• U.S. time zone map
• History of U.S. time zones and UTC conversion
• Canada time zone map
• Time zones for major world cities
• Official times across Canada
• [http://time.gov/timezone.cgi?Atlantic/s/-4/java The official U.S. time for the Atlantic Time Zone (no DST)

References