IST is 5.30 hours ahead of UTC. UTC (Coordinated Universal Time) is the prime time standard by which the world regulates the clocks and time. It is about 1 second of mean solar time at 0 degrees longitude.
Whereas Indian Standard Time is calculated on the basis of 82.5° E longitude at Shankargarh Fort in Allahabad district, so that it would be as close to UTC +5:30 as possible.
For every 15° longitude there is a difference of one hour. India spans longitudes of 68° at the western end and 98° at the eastern boundary and as there is a difference of one hour for every 15° of longitude, the two extremes differ by two hours. Thus, when the sun sets at 4 p.m. in Kohima, it sets at 6 p.m. in Porbunder. IST was fixed in 1906 midway at 82.5°, or 5/ hours ahead of Greenwich Mean Time (GMT). Periodically, there are demands from the Northeast region for a separate time zone so that the clocks there may be advanced by an hour.
For every 15° longitude there is a difference of one hour. India spans longitudes of 68° at the western end and 98° at the eastern boundary and as there is a difference of one hour for every 15° of longitude, the two extremes differ by two hours. Thus, when the sun sets at 4 p.m. in Kohima, it sets at 6 p.m. in Porbunder. IST was fixed in 1906 midway at 82.5°, or 5/ hours ahead of Greenwich Mean Time (GMT). Periodically, there are demands from the Northeast region for a separate time zone so that the clocks there may be advanced by an hour.
A few years ago, then Assam Chief Minister Tarun Gogoi, frustrated with the decision of the Centre not to have a separate Northeast time, unilaterally decided that Assam would follow ChaiBagaan time. Bagaan time or tea time is a reference to an informal practice followed in tea gardens in Assam which is an hour ahead of IST. It alerts us to the fact that there is indeed a long history of the application of different time zones in India.
Creation of two time zones for a nation like India will end up with unimaginable chaos creating a massive mess in day to day life of 1.2 billion people.
Proposal of advancing IST by half an hour avoids the problems and provides maximum energy saving during evening hours when the utilities fail to supply continuous power. Load shedding is common all over the country and power and energy shortages amount to 11 percent and 12 percent respectively.
The Indian government has setup many committees to assess the necessity of dual time zones and advancing IST, however, all the reports suggested to continue the existing time zone. (source: The Hindu, Internet)