How many hours is MST behind PHST?
As abbreviations, PHST is always 15 hours ahead of MST: MST is UTC−7 and PHST is UTC+8. To convert, add 15 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 PHST is 14 hours ahead of MST.
When the MST to PHST time difference changes
For most of the year PHST is 14 hours ahead of MST. From 1 November to 31 December 2026, PHST is 15 hours ahead 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 | PHST vs MST | Length |
|---|---|---|
| 8 March 2026 to 31 October 2026 | 14 hours ahead | 238 days |
| 1 November 2026 to 31 December 2026 | 15 hours ahead | 61 days |
| 1 January 2027 to 13 March 2027 | 15 hours ahead | 72 days |
| 14 March 2027 to 6 November 2027 | 14 hours ahead | 238 days |
| 7 November 2027 to 31 December 2027 | 15 hours ahead | 55 days |
Calling hours for MST and PHST
- When PHST is 14 hours ahead of MST: no shared 09:00 to 17:00 hours; try 17:00 in MST (07:00 in PHST).
- When PHST is 15 hours ahead of MST: no shared 09:00 to 17:00 hours; try 17:00 in MST (08:00 in PHST).