Time and longitude are related. As the earth rotates, every place experiences the phenomena of sunrise, noon and sunset. One hour of time is equivalent to 15° of longitude. This can be calculated and understood from the fact that the earth completes one rotation on its axis in 24 hours, so in each hour , it covers 15° of longitude to cover 360°of longitude in total.This also means that 1° of longitude is covered every 4 minutes during the daily rotation of the Earth. This equality forms the basis of all calculations concerning time belts of the globe.
- The time of the day at a place as indicate by the position of the sun is local time, i.e., it is the mean solar time based on the local meridian.
- Local time implies the time of a place determined on the basis of apparent movement of the sun.
- Local time, as the name suggest is the time in a specific region, which is expressed in relation to the line of longitude passing through it. It is the time, reckoned on the basis of the meridian running through a particular place.
- Places on the same longitude have same local time
- Standard time is the synchronization of clocks within a geographical area or region to a single time standard, rather than using solar time or a locally chosen meridian (longitude) to establish a local mean time standard.
- Standard time refers to the fixed time for places falling in the same meridian, set in a country by law.
- Standard time is used to mean the reference time for a particular area. It is the local time of the standard meridian passing through the region or country
- Places on the same longitude have different standard time.
- A time zone is an area in the world recording the same time. As it takes the earth 24 hours to make one rotation.
- Standard Fleming, a Canadian, suggested dividing the earth into 24 time zones.
- In order to distinguish the direction of these zones, the time for all places east of Greenwich is designated fast, and the time for all places west of Greenwich is designated slow.
- The Greenwich meridian at 0° longitude passes through Greenland Sea and Norwegian sea, and the countries of the United Kingdom, France, Spain, Algeria, Mali, Burkina Faso and Ghana, and then through the South Atlantic Ocean.
International Date Line :
- The International Date Line is located halfway around the world from the prime meridian (0° longitude) or about 180° east (or west) of Greenwich, London, UK, the reference point of time zones. It is also known as the line of demarcation.
- It was decided at the International Meridian Conference in 1884 in Washington, D.C. where 26 countries attended.
- The dateline runs from the North Pole to the South Pole and marks the divide between the Western and Eastern Hemisphere.
- It is not straight but zigzags to avoid political and country borders and to not cut some countries in half.
- It passes through the Arctic Ocean, Chukchi sea, avoids Wrangle Island and the Russian landmass, passes through Bering Strait, veers again to avoid the Aleutian Islands, and goes through the Pacific Ocean.
- A few degrees south of the equator the date line has shifted 7.5 °eastward, avoiding Fiji and Tonga island groups which have the same days as New Zealand.