Why does the standard meridian of a country become the time zone?
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Indian Standard Time is calculated on the basis of 82.5' E longitude, in Mirzapur, Uttar Pradesh, which is nearly on the corresponding longitude reference line.
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In 1878, Sir Sandford Fleming (1827–1915) developed the system of worldwide time zones that we still use today. He proposed that the world be divided into 24 time zones, each spaced 15º (fifteen degrees) of longitude apart (like 24 sections of an orange). He came to this idea because Earth completes a rotation every 24 hours and there are 360º of longitude, so each hour Earth rotates 1/24th of a circle or 15º.
As with many new ideas, his solution was not immediately embraced. Railroad companies in the U.S. finally began using Sir Fleming's standard time zones on November 18, 1883. An International Prime Meridian Conference was held in Washington, DC, in 1884 to standardize time around the world and select the Prime Meridian, or the meridian that is designated 0º from which all other longitudes are measured (often referred to as Greenwich Mean Time or GMT, because the place they chose as the Prime Meridian was Greenwich, England). The International Date Line, the imaginary line where travellers change from one date to another, is located at roughly 180º, exactly halfway around the world from Greenwich (conveniently drawn through the Pacific Ocean so no countries are divided into separate days).
According to international convention the longitudinal difference between two time meridians should be a multiple of 7.5 degrees, so that time difference is always in half hours or full hours (7.5 deg * 4 min/deg = 30 minutes).
To find the time meridian of a country, take the westernmost longitude and the easternmost longitude of that country, take the mean, and find the nearest multiple of 7.5 degree.
As India's longitudinal extent is from 68° 7' 53" E to 97° 24' 47" E.
Nearest multiple of 7.5° is 82.5°.
So 82"30 minutes east has been selected as the
As with many new ideas, his solution was not immediately embraced. Railroad companies in the U.S. finally began using Sir Fleming's standard time zones on November 18, 1883. An International Prime Meridian Conference was held in Washington, DC, in 1884 to standardize time around the world and select the Prime Meridian, or the meridian that is designated 0º from which all other longitudes are measured (often referred to as Greenwich Mean Time or GMT, because the place they chose as the Prime Meridian was Greenwich, England). The International Date Line, the imaginary line where travellers change from one date to another, is located at roughly 180º, exactly halfway around the world from Greenwich (conveniently drawn through the Pacific Ocean so no countries are divided into separate days).
According to international convention the longitudinal difference between two time meridians should be a multiple of 7.5 degrees, so that time difference is always in half hours or full hours (7.5 deg * 4 min/deg = 30 minutes).
To find the time meridian of a country, take the westernmost longitude and the easternmost longitude of that country, take the mean, and find the nearest multiple of 7.5 degree.
As India's longitudinal extent is from 68° 7' 53" E to 97° 24' 47" E.
Nearest multiple of 7.5° is 82.5°.
So 82"30 minutes east has been selected as the
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