Because some countries, islands and states do not want to be divided into several zones, the zones' boundaries tend to wander considerably from straight north-south lines. The international dateline was drawn to generally follow the 180 meridian in the Pacific Ocean. The 24 standard meridians, every 15 east and west of 0 at Greenwich, England, were designated the centers of the zones. C., applied the same procedure to zones all around the world. On November 1, 1884, the International Meridian Conference in Washington, D. At noon, on November 18, 1883, telegraph lines transmitted GMT time to major cities where authorities adjusted their clocks to their zone's proper time. That year, the United States was divided into four time zones roughly centered on the 75th, 90th, 105th, and 120th meridians. Until 1883 most railway companies relied on some 100 different, but consistent, time zones. The problem of keeping track of over 300 local times was overcome by establishing railroad time zones. Until the 1860s most cities relied upon their own local “sun” time, but this time changed by approximately one minute for every 12 miles traveled east or west. Time zones did not become necessary in the United States until trains made it possible to travel hundreds of miles in a day. The DST runs from 2 pm on the 2nd Sunday in March to 2 am on the first Sunday in November.Source: National Institute of Standards and Technology Physics Laboratory The Daylight Saving Time (DST) is observed in the whole of US states and territories except in Hawaii, Puerto Rico, American Samoa, US Virgin Island, and Arizona (observed only in Navajo Nation). For instance, Howland Island and Baker Island use UTC-12:00 and are sometimes assigned Anywhere on Earth (AoE). The US also possesses outlying islands which do not observe any of the nine time zones. The US territories observe Samoa Time Zone (American Samoa), Atlantic Time Zone (US Virginia Islands and Puerto Rico), and Chamorro Time Zone (the Northern Mariana Islands and Guam). The state of Alaska observes Alaskan Time Zone (UTC-09:00), while Hawaii and parts of the Aleutian Islands have Hawaii-Aleutian Time Zone (UTC-09:00). For instance, Eastern Time refers to EST or EDT. The time zones observed by the 48 states use generic names, without highlighting the difference between DST and standard time designations. The DST is observed in all of the contiguous states except Arizona (observed only in the Navajo Nation). Washington, Nevada, California, and parts of Oregon and Idaho observe Pacific Time Zone (UTC-07:00) while the states straddled by the Rocky Mountains and Great Plains’ western quarter have Mountain Time Zone (UTC-06:00). The second time zone on the contiguous US is the Central Standard Time (UTC-05:00), observed fully by ten states and partly by the other ten states occupying the Mississippi Valley, Gulf Coast, and parts of the Great Plains. However, Indiana, Florida, Kentucky, Tennessee partially use this time zone. All or most of the 23 states in the eastern US, including those on the Atlantic coast, observe Eastern Time Zone (UTC-04:00). These states fall within four time zones. The contiguous US comprises 48 states located within continental North America. In it, he proposed 24 time zone of 1 hour that he describe has longitudinal days. That year, he published the idea in his book Miranda. Quirico Filopanti, an Italian mathematician, proposed the first worldwide time zones in1858. The Department of Transportation regulates the DST and time zone boundaries in the US. The meridian of Rome and the first time zone world map. The contiguous US observes four time zones, while Hawaii, Alaska, and each of the five territories has its time zone. From west to east, the nine US time zones are Chamorro Standard Time (UTC+10), Samoa Standard Time, Hawaii-Aleutian Standard Time (HST), Alaskan Standard Time (AKST), Pacific Standard Time (PST), Mountain Standard Time, Central Standard Time, Eastern Standard Time (EST), and Atlantic Standard Time (AST). By Law, the United States of America and its territories use nine time zones, with most of the county observing DST (daylight saving time) for much of spring, fall, and summer months.
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