HST to MDT Time Converter
MDT is 4 hours ahead of HST. HST is UTC-10:00, and MDT is UTC-6:00.
Best Time to Call Between HST and MDT
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 MDT. That's a 4-hour window.
both at work HST only MDT only neither — hours along the strip are HST.
Common Times Converted
HST on the left, MDT on the right.
HST to MDT: Full 24-Hour Conversion Table
Shaded rows are working hours; the darker shade marks the hours when both zones are at work.
| HST | MDT | 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 | MDT only |
| 6:00 AM | 10:00 AM | MDT only |
| 7:00 AM | 11:00 AM | MDT only |
| 8:00 AM | 12:00 PM | MDT 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 MDT 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.
MDT — Mountain Daylight Time
Denver, Salt Lake City, Calgary, Edmonton. Standing at UTC-6:00 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.
Because Arizona does not follow it, MDT is the half of the year when Phoenix and Denver read the same clock despite being in different zones.
What This Means in Practice
This gap is not fixed
MDT 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 MDT
Frequently Asked Questions
What is the time difference between HST and MDT?
MDT is 4 hours ahead of HST.
What is 9:00 AM HST in MDT?
9:00 AM HST is 1:00 PM MDT.
What are the best hours to schedule a call between HST and MDT?
Between 9:00 AM and 1:00 PM HST, which is 1:00 PM to 5:00 PM MDT. Both sides are inside normal business hours through that window.
Does the difference between HST and MDT change during the year?
Yes. MDT 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.