How many hours is HST behind MST?
As abbreviations, MST is always 3 hours ahead of HST: HST is UTC−10 and MST is UTC−7. To convert, add 3 hours.
Check which label you actually need: MST (Mountain Time is on MDT today). A time written with an abbreviation that is not in use is usually meant as the local time, so convert between the places instead: right now MST is 4 hours ahead of HST.
When the HST to MST time difference changes
For most of the year MST is 4 hours ahead of HST. From 1 November to 31 December 2026, MST is 3 hours ahead of HST instead, because the two places change their clocks on different dates. Meetings booked by the usual gap land an hour off in those weeks.
| Dates | MST vs HST | Length |
|---|---|---|
| 8 March 2026 to 31 October 2026 | 4 hours ahead | 238 days |
| 1 November 2026 to 31 December 2026 | 3 hours ahead | 61 days |
| 1 January 2027 to 13 March 2027 | 3 hours ahead | 72 days |
| 14 March 2027 to 6 November 2027 | 4 hours ahead | 238 days |
| 7 November 2027 to 31 December 2027 | 3 hours ahead | 55 days |
Best time for a meeting between HST and MST
- When MST is 4 hours ahead of HST: 4 shared office hours, 09:00 to 13:00 in HST (13:00 to 17:00 in MST).
- When MST is 3 hours ahead of HST: 5 shared office hours, 09:00 to 14:00 in HST (12:00 to 17:00 in MST).