There is no overlap between 09:00–18:00 working days in these two places.
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.
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
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).
Frequently asked questions about MST and PHST time
How many hours ahead is PHST of MST?
PHST (UTC+8) is 15 hours ahead of MST (UTC−7).
Does the time difference between MST and PHST change?
Yes. It is usually 14 hours ahead, but changes when one side moves its clocks: 15 hours ahead from 1 November to 31 December 2026; 15 hours ahead from 1 January to 13 March 2027.