Advance Indian Standard Time by half an hour

THIRTY MINUTES: The energy benefits of advancing IST accrue for the entire year throughout the country.   | Photo Credit: TONY KARUMBA

Most Indians are not particularly worried about Indian Standard Time (IST), except for those who live in the Northeast where the sun rises around 4 a.m. in summer, and gets dark well before 4 p.m. in winter. Those of us who have to make overseas long distance calls and get into trouble with fractions are not even aware that we belong to a minority (three per cent) of regions whose standard times are fractional hours off from GMT.

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.

There is a general misconception among those who worry about saving energy — such as the Planning Commission — that dividing the country into time zones will save “a lot of energy.” The savings are almost always described by adjectives, for very few have estimated correctly the amount of savings that may accrue by altering IST or creating two time zones. There is also the practice in several countries, of “Daylight Saving Time” (DST), wherein the time in summer is advanced (or the clocks put forward) by one hour and retracted during winter. This enables people to enjoy sunlight longer in summer and avoid the inconveniences of late sunrises and early sunsets during winter.

Load demand data

Our proposal for India is to introduce neither time zones nor DST, but to advance IST by half an hour to being six hours ahead of GMT, once and permanently. Such a suggestion has been made before, but until now no one has computed the energy savings that would accrue as a result using a correct model and dependable data. Our fairly rigorous method has been vetted by national and international experts and is based on data on load demand every minute for two years at five electrical zones of India provided by the Power Grid Corporation of India. The Bureau of Energy Efficiency provided financial support for the study.

Problems of time zones

India has a huge population; if the country were divided into two time zones, there would be chaos at the border between the two zones. It would mean resetting clocks with each crossing of the time zone. There is scope for more dangerous kinds of confusion. Railway signals are not fully automated and many routes have single tracks. Trains may meet with major accidents owing to human errors. Just one such accident would wipe out any benefits resulting from different time zones in the country.

Partitioning the already divided country further into time zones may also have undesirable political consequences. Moreover, our research shows that the energy saving from creating two time zones is not particularly large.

Problems of DST

As is known, the sun always rises at 6 a.m. on the Equator and sets at 6 p.m. irrespective of the season. It is the tilt of the axis round which the earth rotates by 23.5°, that causes the length of days and nights to change as we go further away from the equator towards the north or the south. At the poles the sun does not set for six months and does not rise for six months. In tropical countries, the duration of light and darkness over the seasons does not vary widely. If we were to introduce DST in India, the inconvenience of time adjustment during summer and winter months would involve the whole country, happening twice a year, with marginal benefits. The possibilities of rail accidents would still be high. Even in the U.S. and Canada, road accidents increase discernibly in the days immediately following the change.

Advance IST by half an hour.

Our proposal of advancing IST by half an hour avoids the problems apprehended in the other two proposals (of time zones and DST) but 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 per cent and 12 per cent respectively.

How is energy saved?

Energy is saved by longer use of sunlight and consequently less use of energy for lighting. The demand for electricity goes up in the morning for water heating and increases again in the evening for five to six hours, mainly for lighting, declining as people turn off lights and go to bed. The advancement of IST by half an hour only is unlikely to alter their habits and a person waking at 7 a.m. and going to bed at 11 p.m. will continue to do so, but advanced 7 a.m. is unaltered 6.30 a.m. when the sun is already up in most parts of the country, and 11 p.m. is the same as unaltered 10.30 p.m. In other words, people all over India will go to bed and wake up half an hour before they presently do and thus their waking hours will be more aligned to the daily cycle of sunshine. One assumption of course is that office times and factory times remain unaltered. It needs to be understood that people switch on lights not by looking at the watch but by the descending darkness after sunset. If on a particular day it got dark at 6 p.m., in say Mumbai, it will still get dark at the same time but the watch would show 6.30, since it has been put forward by half an hour.

Assuming lights kept turned on for five hours from 6 to 11 (bedtime) now will be kept on from 6.30 to 11 (bedtime), that is for 4/ hours, the half-hour saving on lighting leads to an energy saving of 2.3 billion units of energy per year for the country. This saving amounts to almost 18 per cent of evening peaking energy use, and would partly reduce the deficit that we presently suffer. The savings from time zones and DST are significantly less — the saving due to time zones comes from the eastern zone only, and for DST from half the year. The half-hour advancement of IST provides benefits for the whole country for the whole year. Besides saving energy, a longer sunlit evening would reduce street crimes. Traffic accidents may also come down to some extent.

By advancing IST by half an hour we meet the legitimate demands of the Northeast halfway without any of the inconveniences of time zones or DST. So why not advance it by an hour? It would cause complaints from the northwest about the inconvenience of later winter sunrises.

( D.P. SenGupta was formerly a professor at the Indian Institute of Science and is currently a visiting professor of the National Institute of Advanced Studies in Bangalore. Dilip R. Ahuja is ISRO Professor at NIAS. The Bureau of Energy Efficiency commissioned a study by them on quantifying energy savings through advancing IST, based on a paper published by them in Current Science in 2007. Their final report was submitted to the BEE in September 2011.)

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Printable version | Nov 28, 2021 3:23:17 PM |

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