The world is divided into time zones measured as an offset from Coordinated Universal Time (UTC/GMT), so that clocks roughly match daylight hours in each region. India uses a single time zone, Indian Standard Time (IST), which is fixed at UTC+5:30 — a half-hour offset chosen because India spans a wide range of longitude and a half-hour adjustment better centres the country's time around solar noon.

This matters whenever you're scheduling something across borders: an online exam, a video call with an international client, a webinar, or checking when a US-based university's application portal opens. EST (US Eastern Standard Time) is typically 9.5 or 10.5 hours behind IST, depending on whether the US is observing daylight saving time.