Which zone this page means. GMT and UTC are the same offset but not the same thing: GMT is a time zone, UTC is a time standard. The United Kingdom is on GMT in winter and BST (UTC+1) in summer. IST means India Standard Time (UTC+5:30), Irish Standard Time (UTC+1) and Israel Standard Time (UTC+2). This page means the Indian zone, which is one of the few on a half-hour offset.
GMT is behind IST by 5.5 hours today
On 19 August 2026, Greenwich Mean Time is on GMT at UTC+00:00 and India Standard Time is on IST at UTC+05:30. The gap between them is 5.5 hours, with IST ahead. So 9:00 am in GMT is 2:00 pm in IST, and 5:00 pm in GMT is 10:00 pm in IST. Going the other way, see IST to GMT.
The gap is not constant, and that is the part that catches people out
Neither zone observes daylight saving, so this is one of the few pairs where the offset really is constant all year. That is unusual: most gaps between named zones move by an hour twice a year, and by two hours during the weeks when the two ends change on different dates.
When you can actually both be at work
Taking a working day as 9:00 am to 5:00 pm local at each end, there are 3 overlapping hours in a normal day. In GMT that window runs from 9:00 am to 12:00 pm, which is 2:00 pm to 5:00 pm in IST. Anything outside it needs one side to start early or finish late.
Zone rules are set by legislation and change, sometimes at short notice. This page is built against tzdata 2026a, last reviewed 2026-08-18. Quarterly. Zone rules change by legislation, sometimes at short notice. Version and review date are shown on every zone page. The converter above reads your browser's own copy of the zone database, so if a rule has changed since this page was built the live answer follows the new rule.
Every convention used above — whether the start date counts, how month ends are clamped, which holidays close an office — is written out on the methodology page, including the daylight-saving rules behind the 5.5-hour gap above.