HST to MST
+3hHST
HSTSOURCEMST
MSTGreen rows indicate typical business hours (9 AM - 5 PM)
HST and MST on the World Map
The map below highlights the HST (Hawaii Standard Time) and MST (Mountain Standard Time) timezone regions across the globe.
HST – Hawaii Standard Time
UTC-10:00Hawaii Standard Time (HST) is the time zone for the Hawaiian Islands, 10 hours behind UTC.
- •Hawaii does not observe daylight saving time.
- •HST is 5 hours behind EST in winter and 6 hours behind EDT in summer.
- •Hawaii is one of only two US states that don't observe DST (the other is Arizona).
MST – Mountain Standard Time
UTC-07:00Mountain Standard Time (MST) is the time zone for the Mountain region of North America, 7 hours behind UTC.
- •Arizona does not observe daylight saving time, staying on MST year-round.
- •The Navajo Nation in Arizona does observe DST, unlike the rest of the state.
- •Denver, the 'Mile High City', is the largest city fully in MST.
- •MST covers 6 US states entirely and parts of several others.
HST to MST Time Difference – Complete Guide
HST runs on Hawaii Standard Time (HST) at UTC-10:00. MST runs on Mountain Standard Time (MST) at UTC-07:00. That puts HST 3 hours ahead of MST — a difference of +3h at the current offsets.
In practice, when it is 9:00 AM in HST it is 12:00 PM in MST. Midnight in HST is 3:00 AM in MST. Neither zone observes daylight saving time, so the offset between them stays constant all year.
HST to MST time conversion table
| HST (HST) | MST (MST) | Day |
|---|---|---|
| 12:00 AM | 3:00 AM | same day |
| 6:00 AM | 9:00 AM | same day |
| 7:00 AM | 10:00 AM | same day |
| 8:00 AM | 11:00 AM | same day |
| 9:00 AM | 12:00 PM | same day |
| 12:00 PM | 3:00 PM | same day |
| 3:00 PM | 6:00 PM | same day |
| 5:00 PM | 8:00 PM | same day |
| 6:00 PM | 9:00 PM | same day |
| 9:00 PM | 12:00 AM | next day |
Why people convert HST to MST time
- Scheduling a call from HST to MST: a 10:00 AM start in HST lands at 1:00 PM in MST, so you can confirm the slot without doing the arithmetic yourself.
- Finding shared working hours: both HST and MST are inside the 9-to-5 working day between 9:00 AM and 2:00 PM HST time (12:00 PM–5:00 PM MST). That is roughly 5 hours of usable overlap.
- Keeping family and friends in sync: knowing that 8:00 PM in HST is 11:00 PM in MST makes it easy to avoid calling at 3 AM.
- Always state the zone abbreviation, not just the hour. "3:00 PM HST" is unambiguous; "3 PM" across a +3h gap is not.
- Block 9:00 AM–2:00 PM HST as the recurring meeting window if you work primarily from HST and need MST colleagues present.
About HST (Hawaii Standard Time)
Hawaii Standard Time (HST) is used in the state of Hawaii and does not observe daylight saving time. This makes HST one of the most consistent time zones in the US. The Hawaiian Islands are among the last places on Earth to see a new calendar day.
About MST (Mountain Standard Time)
Mountain Standard Time (MST) covers the Rocky Mountain region of the United States and Canada. Arizona is notable for not observing daylight saving time, staying on MST year-round (except the Navajo Nation). The time zone includes major cities like Denver, Phoenix, Calgary, and Salt Lake City. During summer, most areas switch to Mountain Daylight Time (MDT, UTC-06:00).
Best time to call between HST and MST
Both HST and MST sit inside the 9 AM – 5 PM working day between 9:00 AM–2:00 PM HST, which is 12:00 PM–5:00 PM MST. That gives roughly 5 hours of shared time — the safest window for a live call or meeting.
Business hours overlap
HST and MST share 5 hours of working-hours overlap (9:00 AM–2:00 PM HST), so scheduling a live meeting is straightforward.
HST is 3 hours ahead of MST (HST UTC-10:00 → MST UTC-07:00). The shared working window is 9:00 AM–2:00 PM HST. Remember to re-check around daylight-saving transitions.
🕐 Daylight Saving Time Info
HST
Does not observe DST
MST
☀ Currently in DST
Standard: UTC-07:00 · DST: UTC-06:00
Clocks fall back on Sun, Nov 1, 2026
Learn More About Time
Dive deeper into the fascinating world of timekeeping, time zones, and how they shape our global society:
Frequently Asked Questions
What is the time difference between HST and MST?
HST (HST, UTC-10:00) is 3 hours ahead of MST (MST, UTC-07:00). The gap is currently +3h.
How do I convert HST time to MST time?
Add +3h to HST local time. For example, 9:00 AM in HST is 12:00 PM in MST.
What time is it in MST right now?
MST uses MST at UTC-07:00. Use the live converter at the top of this page — it updates in real time and already accounts for the +3h offset from HST.
What is the best time to call MST from HST?
Call between 9:00 AM and 2:00 PM HST — that maps to 12:00 PM–5:00 PM MST and keeps both parties inside the working day.
Which is ahead, HST or MST?
HST is 3 hours ahead of MST. When it is 12:00 PM in HST it is 3:00 PM in MST.
Does daylight saving time affect the HST–MST difference?
Neither zone observes daylight saving time, so the +3h offset between HST and MST is fixed all year.
Which other cities share HST's time zone?
HST also covers Honolulu, Hilo, Kailua, Pearl City, Kapolei.
Which countries use HST, HST's zone?
HST is used in United States (Hawaii).
Is there a day difference between HST and MST?
Not normally. The +3h gap only pushes the date over for late-evening times.
What is the time difference between HST and MST?
MST is +3h from HST.
What timezone is HST in?
HST operates on its local timezone.
What timezone is MST in?
MST operates on its local timezone.
Which countries use HST (Hawaii Standard Time)?
HST is used in United States (Hawaii).
Does HST observe daylight saving time?
No, HST does not observe daylight saving time and remains at UTC-10:00 year-round.
What are some interesting facts about HST?
Hawaii does not observe daylight saving time. HST is 5 hours behind EST in winter and 6 hours behind EDT in summer.
Which cities are in the MST timezone?
Major cities in the MST timezone include Denver, Phoenix, Salt Lake City, Calgary, Edmonton, Albuquerque, El Paso, Tucson.
What is the UTC offset for MST?
Mountain Standard Time (MST) is at UTC-07:00. During daylight saving time, it shifts to MDT.
What should I know about the MST timezone?
Arizona does not observe daylight saving time, staying on MST year-round. The Navajo Nation in Arizona does observe DST, unlike the rest of the state.
When is it midnight in HST, what time is it in MST?
When it is 12:00 AM (midnight) in HST (HST), it is +3h later in MST (MST).
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See every conversion from HST →·See every conversion from MST →