No daylight saving, one zone, half an hour off
India Standard Time is UTC+05:30 all year, with no seasonal change, across the entire country. The thirty-minute offset comes from IST being set to the 82.5°E meridian, chosen because it runs near Allahabad and sits neatly between the country's eastern and western extremes.
The two-time-zone debate
India spans roughly 30 degrees of longitude — about two hours of solar time — yet runs one clock. In the northeast, sunrise in summer can come before 4:30 a.m. and sunset before 5 p.m., which wastes daylight and, by several studies, energy. Assam has argued for a separate "Bagan time" for decades, and the government's own National Physical Laboratory has recommended a second zone. It has never been adopted, largely over fears of railway scheduling errors and administrative confusion.
Wartime exceptions
India briefly used daylight saving during the 1962 conflict with China and again in 1965 and 1971 during the wars with Pakistan. Those are the only instances. Tea plantations in Assam have long kept their own unofficial "chai bagan time", an hour ahead of IST, to match the working day to the sun.