American and Canadian railroads first began establishing standard time in 1883. However, standard time in time zones wasn't officially made into a law until the Standard Time Act of March 1918. This act gave authority to the Interstate Commerce Commission to define the boundaries of these time zones, a power which eventually passed to the Department of Transportation. The boundaries of the time zones have changed substantially over the years and changes still occur. These boundaries are laid out in the Code of Federal Regulations.
While the majority of Alaska is located in the Alaskan time zone, the western parts of the Aleutian Islands, which extend far out into the Pacific, are located in the Hawaii-Aleutian time zone. Hawaii-Aleutian Standard Time is 10 hours behind Coordinated Universal Time, or one hour behind the mainland territory of the state. Mainland Alaska is one hour behind Pacific Standard Time.
Alaskan time zones have only been observed in this current form since 1983. Originally dating to the Standard Time Act of 1918, Alaskan Standard Time was designated as UTC-10. However, the Uniform Time Act of 1966 renamed this zone Alaskan-Hawaiian Standard Time. Back in 1966, places like Juneau observed Pacific Time or UTC-8; the interior observed UTC-10; and the Aleutians observed UTC-11. UTC-9 was known as Yukon Standard Time for Canada's Yukon Territory. However in 1975, the Yukon Territory moved to Pacific Time, meaning UTC-9 was effectively observed by no one. Thus in 1983, Alaska adopted UTC-9, and by U.S. law, Yukon Standard Time became Alaskan Standard Time, and the Alaska-Hawaiian time zone became the Hawaii-Aleutian time zone.
The state of Florida is predominantly located in the Eastern time zone. The state's major cities and the majority of its population are located there. However, the western part of the Florida panhandle is located in the Central time zone. The boundary runs roughly along the Apalachicola River and then the border between Gulf County and Bay County. Important cities in Florida located in the Central time zone include Pensacola and Panama City.