IST to MST

About India Standard Time

India keeps one clock, UTC+5:30, across a country spanning about 29 degrees of longitude — the sun rises nearly two hours earlier in Arunachal Pradesh than in Gujarat on the same clock. The half-hour offset means most conversions from India land on the half hour rather than the hour. Sri Lanka keeps the same time.

Cities on this clock: Mumbai, Delhi, Bangalore, Hyderabad, Chennai, Kolkata, Pune, Ahmedabad.

Watch out: IST is also Israel Standard Time (UTC+2) and Irish Standard Time (UTC+1). This page is the Indian one.

About Mountain Time

Mountain Time is UTC−7 as MST and UTC−6 as MDT, on the same transition dates as the rest of the United States. Arizona is the exception worth knowing: almost all of it stays on MST all year, so for the eight months the rest of the zone is on MDT, Phoenix keeps the same clock as Los Angeles rather than Denver.

Cities on this clock: Denver, Salt Lake City, Calgary, Edmonton.

How the difference is worked out

The gap between India Standard Time and Mountain Time is not one number. The two zones change their clocks on different dates, so for part of the year the difference is 11 hours 30 minutes and for the rest it is something else — the table above lists each stretch of 2026 with the date it starts and which country's clocks moved.

With both zones on their own standard time — daylight saving not in force anywhere — Mountain Time is 12 hours 30 minutes behind India Standard Time. That figure never changes; everything else on this page follows from it plus whichever clocks have moved.

Every figure here comes from the IANA time zone database via your browser's own Intl engine, using the zone ids Asia/Kolkata and America/Denver. Nothing is looked up on a server and nothing about your visit is recorded.