HST to MST Time Converter
MST is 4 hours ahead of HST. HST is UTC-10:00, and The US Mountain states are currently on MDT (UTC-6:00).
Best Time to Call Between HST and MST
Both zones are inside normal business hours between 9:00 AM and 1:00 PM HST — that's 1:00 PM to 5:00 PM MST. That's a 4-hour window.
both at work HST only MST only neither — hours along the strip are HST.
Common Times Converted
HST on the left, MST on the right.
HST to MST: Full 24-Hour Conversion Table
Shaded rows are working hours; the darker shade marks the hours when both zones are at work.
| HST | MST | Working hours |
|---|---|---|
| 12:00 AM | 4:00 AM | — |
| 1:00 AM | 5:00 AM | — |
| 2:00 AM | 6:00 AM | — |
| 3:00 AM | 7:00 AM | — |
| 4:00 AM | 8:00 AM | — |
| 5:00 AM | 9:00 AM | MST only |
| 6:00 AM | 10:00 AM | MST only |
| 7:00 AM | 11:00 AM | MST only |
| 8:00 AM | 12:00 PM | MST only |
| 9:00 AM | 1:00 PM | Both zones |
| 10:00 AM | 2:00 PM | Both zones |
| 11:00 AM | 3:00 PM | Both zones |
| 12:00 PM | 4:00 PM | Both zones |
| 1:00 PM | 5:00 PM | HST only |
| 2:00 PM | 6:00 PM | HST only |
| 3:00 PM | 7:00 PM | HST only |
| 4:00 PM | 8:00 PM | HST only |
| 5:00 PM | 9:00 PM | — |
| 6:00 PM | 10:00 PM | — |
| 7:00 PM | 11:00 PM | — |
| 8:00 PM | 12:00 AM next day | — |
| 9:00 PM | 1:00 AM next day | — |
| 10:00 PM | 2:00 AM next day | — |
| 11:00 PM | 3:00 AM next day | — |
What HST and MST Actually Are
HST — Hawaii Standard Time
Honolulu and the rest of Hawaii. Standing at UTC-10:00 as written, and the region does not change its clocks, so that offset holds all year. Hawaii does not observe daylight saving, so this offset holds all year.
Hawaii dropped daylight saving in 1967 and never resumed it. Being close to the equator, its daylight barely varies across the year, so there is little to gain.
MST — Mountain Standard Time
Denver, Salt Lake City, Calgary — and Phoenix year-round. Standing at UTC-7:00 as written, and the region does change its clocks, so its live offset moves by an hour twice a year. The next change is on Sunday, November 1, 2026, to MST. Arizona stays on MST all year, so Phoenix and Denver are an hour apart for eight months and identical for four.
Arizona has stayed on MST year-round since 1968 — the Navajo Nation within it does observe daylight saving, making the state a patchwork.
What This Means in Practice
This gap is not fixed
MST changes its clocks and HST does not, so the difference between them moves by an hour twice a year. A recurring meeting set now will drift for one side from Sunday, November 1, 2026 unless someone resets it.
Major Cities in Each Zone
Cities on HST
Cities on MST
Frequently Asked Questions
What is the time difference between HST and MST?
MST is 4 hours ahead of HST. That is the live figure. Taken strictly as written, the gap between HST and MST is 3 hours — the two differ because at least one of these regions is currently on daylight saving.
What is 9:00 AM HST in MST?
9:00 AM HST is 1:00 PM MST.
What are the best hours to schedule a call between HST and MST?
Between 9:00 AM and 1:00 PM HST, which is 1:00 PM to 5:00 PM MST. Both sides are inside normal business hours through that window.
Does the difference between HST and MST change during the year?
Yes. MST observes daylight saving and HST does not, so the gap shifts by an hour at least twice a year. The next clock change is on Sunday, November 1, 2026.
Does HST always mean Hawaii Standard Time?
Hawaii does not observe daylight saving, so this offset holds all year.
Does MST always mean Mountain Standard Time?
Arizona stays on MST all year, so Phoenix and Denver are an hour apart for eight months and identical for four.