What Is a Time Zone? – The Earth is divided into 37 different time zones. Each zone is a region in which a uniform standard time is observed for legal, commercial, and social purposes.
QUESTIONS: What Is a Time Zone? – Many time zones are offset from each other by exactly an hour. With there being 24 hours in a day, it seems like it would make sense for there to be 24 time zones.
History of Time Zones – A few hundred years ago, each individual town kept track of their own time. When railroads began to carry people long distances across the country, however, train schedules became confusing because there was a different official time in every town where the trains stopped.
QUESTIONS: History of Time Zones – Although most countries today still use some variation of Fleming's system, some don’t. All of China uses a single time zone eight hours ahead of UTC, though they span five.
Time Zones and Railroads – A few hundred years ago, individual towns kept track of time independently, based on the sun. When the sun was at its zenith, it was noon. Each town set their clocks to noon every day, and the town clock was the official time by which all other clocks and pocket watches in town were set.
QUESTIONS: Time Zones and Railroads – The first country to set an entire region to a standard time was Britain. Dr. William Hyde Wollaston (1766-1828) is credited with coming up with the idea, which was made popular by Abraham Follett Osler (1808-1903).
Daylight Savings Time in the U.S. – The concept of Daylight Savings Time began during World War I as a strategy to conserve the fuel that produced electric power. Germany and Austria were the first to implement daylight savings in 1916 by moving their clock hands forward for one hour beginning on April 30, and remaining so until the following October.
QUESTIONS: Daylight Savings Time in the U.S. – Daylight savings was adopted in the U.S. on March 19, 1918 as part the law implementing standardized time zones, and Daylight Savings Time was first observed in the U.S. for seven months in 1918 and 1919.
Coordinated Universal Time – Coordinated Universal Time, abbreviated UTC. UTC, is the basis for how time is kept throughout the world. UTC itself is not a time, it is a time standard. This means that around the world, timing centers have agreed to synchronize, or coordinate, their time scales.
QUESTIONS: Coordinated Universal Time – Because it does not take the Earth exactly 24 hours to complete one rotation, which is less exact than atomic clocks, UTC was occasionally adjusted in order to keep it in line with the Earth's rotation.
How Many Time Zones Are There? – In 1878, a Canadian named Sir Sandford Fleming suggested dividing the globe into 24 times zones, each one 15 degrees longitude and one hour apart. U.S railroad companies adopted Fleming's time zone system in 1883. In the following year, at an International Prime Meridian Conference in Washington D.C. Greenwich, England was selected as the Prime Meridian (0 degrees longitude), and the 24 time zones were offset from the prime meridian in one hour increments.
QUESTIONS: How Many Time Zones Are There? – There are several reasons that we have 37 time zones and not 24. One reason is because the International Date Line (IDL) creates three more time zones.
Standard Time – Daylight Savings Time refers to the period of time in which clocks are advanced during the summer months in order to make daylight last longer into the evening. Standard time is also known as winter time or normal time.
QUESTIONS: Standard Time – The length of time in which standard time and Daylight Savings Time are in effect are not equal. Standard time is typically shorter. In the U.S. and Canada, standard time is only in effect for about 4.5 months.
The International Date Line – The International Date Line, also known as the line of demarcation, is an imaginary line on the Earth's surface that indicates where one day ends and the next day begins.
QUESTIONS: The International Date Line – The International Date Line stretches from the North Pole down to the South Pole, and provides a conceptual division between the Eastern and Western hemispheres.
Why We Have Time Zones – hough the invention of the chronometer meant that keeping consistently accurate time was now possible, most towns and cities still used sunsets, sunrises, and the position of the sun in the sky to set and keep the local time. Individual localities maintained their own timekeeping.
QUESTIONS: Why We Have Time Zones – So the creation of standardized time zones was driven by the expansion of the transportation and communication industries in the 19th century.
Jet Lag – A circadian rhythm is a natural process that takes place inside of the human body. It is responsible for regulating the sleep-wake cycle, and it repeats approximately every 24 hours.
QUESTIONS: Jet Lag – The SCN is connected to the optic nerve. When your eyes sense changes in daylight, that information is relayed to the SCN, which in turn regulates these biological functions.