Which zone this page means. BST means British Summer Time (UTC+1) and also Bangladesh Standard Time (UTC+6). This page means the British zone, which applies from the last Sunday in March to the last Sunday in October; the rest of the year the United Kingdom is on GMT. MST is standard time only; MDT (UTC-6) applies from March to November. Arizona stays on MST all year.
BST is ahead of MST by 7 hours today
On 19 August 2026, British Summer Time is on BST at UTC+01:00 and Mountain Standard Time is on MDT at UTC-06:00. The gap between them is 7 hours, with MST behind. So 9:00 am in BST is 2:00 am in MST, and 5:00 pm in BST is 10:00 am in MST. Going the other way, see MST to BST.
The gap is not constant, and that is the part that catches people out
British Summer Time is currently observing daylight saving and changes next on 25 October 2026, when clocks go back an hour. Mountain Standard Time is currently observing daylight saving and changes next on 1 November 2026. Because the two zones change on different dates — EU rules for BST and US rules for MST — there are a few weeks each year when the usual gap between them is an hour out. That window is the single most common source of a missed call between these two zones, and it is why a page that quotes only the nominal offset is wrong for part of the year.
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 is 1 overlapping hour in a normal day. In BST that window runs from 4:00 pm to 5:00 pm, which is 9:00 am to 10:00 am in MST. 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 7-hour gap above.