EST to MST

About Eastern Time

Eastern Time is the most populous North American zone and the one most business hours are quoted in. It is UTC−5 as EST and UTC−4 as EDT. Because it changes on US dates rather than European ones, its gap to London and to Central Europe is not constant — there are two short stretches each year when it is an hour narrower than usual, and they are the reason this pair's table has more than one row.

Cities on this clock: New York, Philadelphia, Boston, Miami, Atlanta, Toronto, Montreal, Ottawa.

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

Neither Eastern Time nor Mountain Time moves its clock relative to the other, so mountain time is 2 hours behind eastern time is a rule rather than a fact about one particular year. The hour-by-hour table above holds on every date. The one exception is a few hours on each transition day: the two zones do change their clocks, and not at the same instant, so the gap is briefly an hour off between one switching and the other.

With both zones on their own standard time — daylight saving not in force anywhere — Mountain Time is 2 hours behind Eastern 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 America/New_York and America/Denver. Nothing is looked up on a server and nothing about your visit is recorded.