How many hours is MST ahead of HST?
As abbreviations, HST is always 3 hours behind of MST: MST is UTC−7 and HST is UTC−10. To convert, subtract 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 HST is 4 hours behind of MST.
When the MST to HST time difference changes
For most of the year HST is 4 hours behind of MST. From 1 November to 31 December 2026, HST is 3 hours behind of MST 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 | HST vs MST | Length |
|---|---|---|
| 8 March 2026 to 31 October 2026 | 4 hours behind | 238 days |
| 1 November 2026 to 31 December 2026 | 3 hours behind | 61 days |
| 1 January 2027 to 13 March 2027 | 3 hours behind | 72 days |
| 14 March 2027 to 6 November 2027 | 4 hours behind | 238 days |
| 7 November 2027 to 31 December 2027 | 3 hours behind | 55 days |
Best time for a meeting between MST and HST
- When HST is 4 hours behind of MST: 4 shared office hours, 13:00 to 17:00 in MST (09:00 to 13:00 in HST).
- When HST is 3 hours behind of MST: 5 shared office hours, 12:00 to 17:00 in MST (09:00 to 14:00 in HST).