Why India's Single Time Zone Creates a 2-Hour Daylight Gap Across the Country

India stretches from 68°7' East longitude at Koteshwar in Gujarat to 97°25' East at Kibithu in Arunachal Pradesh. That is a span of roughly 29 degrees. The Earth rotates at 15 degrees per hour, so those two points sit nearly two hours apart in solar time. When the sun climbs over the Brahmaputra valley at 4:30 in the morning local solar time, it is still the middle of the night by the sun's reckoning in the Rann of Kutch. Both places read the same number on their clocks.

India adopted a single time zone, UTC+5:30, at independence. The offset itself is unusual: most countries sit at a whole-hour or half-hour offset from UTC, but India chose a 30-minute split to land IST roughly at the solar noon of the 82°30' East meridian, which passes through Mirzapur in Uttar Pradesh. That meridian was chosen because it runs close to the geographic centre of the country as it existed in 1947. The logic was administrative unity, not astronomical convenience.

In Arunachal Pradesh, Assam, and most of the Northeast, the sun rises before 4 a.m. in summer and sets by 4 p.m. in winter. Workers, farmers, and schoolchildren in those states begin their days in full daylight while the official clock still reads the small hours. Tea garden workers in Assam have operated on an informal time system called Chaibagaan time or Bagan time for over a century, running roughly an hour ahead of IST, because the economics of tea harvesting follow the sun, not New Delhi. That informal offset is not a quirk. It is the population adapting to an astronomical fact the official calendar ignores.

At the western end, the opposite problem holds. In winter, sunset in Ahmedabad arrives well before 6 p.m. IST, but the working day and school schedules are calibrated to a clock that does not reflect that. Energy economists at the National Institute of Advanced Studies in Bengaluru estimated in a widely cited 2001 analysis that the misalignment between solar time and clock time in the Northeast costs the region significant electricity, because artificial lighting is needed in the early morning hours when the sun has already risen, simply because offices and institutions have not yet opened. The figure most quoted from that study is around 2.7 billion units of electricity annually, though the methodology and the number have been contested and should be treated as an order-of-magnitude estimate rather than a settled fact.

The international time zone system is built on a simple geometric principle. The Earth completes one full rotation of 360 degrees in 24 hours, so each hour of time corresponds to 15 degrees of longitude. The standard approach divides the globe into 24 zones, each 15 degrees wide, each offset from UTC by a whole number of hours. In practice, countries bend zone boundaries for political and economic reasons, which is why China, spanning over 60 degrees of longitude, uses a single zone, and why Russia uses eleven.

India's 29-degree span would, under a strict geometric system, fall across two zones: roughly UTC+5 for the west and UTC+6 for the east. A proposal first formally raised by the Planning Commission in 2001 and revisited in academic literature since then suggested exactly this split, with IST remaining for most of the country and a Northeast Time of UTC+6 or UTC+6:30 applying to the seven northeastern states and West Bengal. The proposal was not adopted. The objections were administrative: railway timetables, broadcasting schedules, financial settlement windows, and the political symbolism of a unified national time all weighed against the change.

Solar noon, the moment when the sun reaches its highest point in the sky, is the anchor around which human circadian rhythms evolved. Research in chronobiology, the study of biological time, has established that populations whose clock noon is significantly later than their solar noon tend to show later sleep onset, shorter sleep duration, and higher rates of social jetlag, the chronic misalignment between biological time and social schedules. A 2019 study published in Nature Human Behaviour used data from over 65,000 individuals across Europe and found that each degree of westward longitude within a time zone was associated with measurable shifts in sleep timing and metabolic markers. The effect is not dramatic for any single individual, but across a population the size of the Northeast, it accumulates.

India's eastern states sit at the far end of this effect within their zone. Their solar noon arrives well before their clock noon, meaning the population is, in chronobiological terms, living in a state of permanent mild jetlag relative to the clock. Whether a second time zone would meaningfully improve population health outcomes is a contested question, and no Indian study has yet produced a controlled answer. But the mechanism is established science, not speculation.

The case for a second Indian time zone is not primarily an astronomical argument, even though astronomy supplies its most precise evidence. It is an argument about whose daily life the national clock is calibrated for. The 82°30' East meridian runs through the Hindi heartland. The sun over Itanagar and the sun over Jaisalmer are not the same sun at the same moment, and the people living under each of them know it in their bodies, their farming, and their electricity bills, even when the clock refuses to say so. Whether the administrative cost of splitting the zone is worth paying is a policy question. The astronomy simply makes the case that the cost of not splitting it is not zero, and is not evenly shared.