HST to MST Converter
Convert time between Hawaii Standard Time (HST) and Mountain Standard Time (MST)
Hawaii Standard Time (HST)
Mountain Standard Time (MST)
Time Difference
Mountain Standard Time (MST) is 0 hours ahead of Hawaii Standard Time (HST)
Select Date
Select Time
Quick Reference
| HST | MST |
|---|---|
| 16:00 | 19:00 |
| 18:00 | 21:00 |
| 20:00 | 23:00 |
| 22:00 | 01:00 |
| 00:00 | 03:00 |
| 02:00 | 05:00 |
| 04:00 | 07:00 |
| 06:00 | 09:00 |
| 08:00 | 11:00 |
| 10:00 | 13:00 |
| 12:00 | 15:00 |
| 14:00 | 17:00 |
Top 10 Most Common Time Zones
| Abbreviation | Full Name | UTC Offset | Typical Use |
|---|---|---|---|
| UTC | Coordinated Universal Time | UTC ±0 | Global reference standard (servers, logs, APIs) |
| EST / EDT | Eastern (US) Time | UTC −5 / −4 | New York, Toronto — North American business hub |
| CST / CDT | Central (US) Time | UTC −6 / −5 | Chicago, Dallas — US central business region |
| PST / PDT | Pacific (US) Time | UTC −8 / −7 | San Francisco, Los Angeles — tech industry standard |
| GMT / BST | Greenwich Mean / British Summer Time | UTC 0 / +1 | UK, used globally as a reference with UTC |
| CET / CEST | Central European (Summer) Time | UTC +1 / +2 | Paris, Berlin, Amsterdam — EU business core |
| IST | India Standard Time | UTC +5:30 | India — major IT & outsourcing region |
| CST | China Standard Time | UTC +8 | Beijing, Shanghai — East Asia business hub |
| JST | Japan Standard Time | UTC +9 | Tokyo — finance & tech hub |
| AEST / AEDT | Australian Eastern (Daylight) Time | UTC +10 / +11 | Sydney, Melbourne — APAC regional business |
Why Time Zone Abbreviations Are Ambiguous
Unlike standardized identifiers (like America/New_York or Europe/London from the IANA tz database), abbreviations such as "CST" or "IST" are not globally unique. They can refer to different time zones depending on context — country, region, or even time of year (due to daylight saving time).
Common Ambiguous Time Zone Abbreviations
| Abbrev. | Common Meaning(s) | UTC Offset | Region(s) |
|---|---|---|---|
| CST | Central Standard Time / China Standard Time / Cuba Standard Time | UTC−6 / UTC+8 / UTC−5 | North America, China, Cuba |
| IST | Indian Standard Time / Irish Standard Time / Israel Standard Time | UTC+5:30 / UTC+1 / UTC+2 | India, Ireland, Israel |
| AST | Atlantic Standard Time / Arabia Standard Time | UTC−4 / UTC+3 | Caribbean, Canada, Middle East |
| PST | Pacific Standard Time / Philippine Standard Time | UTC−8 / UTC+8 | North America, Philippines |
| EST | Eastern Standard Time (North America / Australia) | UTC−5 / UTC+10 | North America, Australia |
✅ Best Practice
To avoid ambiguity, always:
- Use IANA tz identifiers — e.g.,
America/New_Yorkinstead of "EST" - Specify UTC offset explicitly — e.g.,
UTC−5when abbreviations must be used - Include the full timezone name — e.g., "Eastern Standard Time (EST)" with UTC offset
Related Time Zone Conversions
About HST to MST Time Conversion
Converting time between Hawaii Standard Time (HST) and Mountain Standard Time (MST) is important for coordinating between Hawaii and the US Mountain region. HST is UTC-10, while MST is UTC-7, making MST 3 hours ahead of HST. Hawaii does not observe daylight saving time, but the Mountain region does, adding complexity to the conversion.
This conversion is vital for business operations between Hawaii and the Mountain states, including Colorado, Utah, Arizona, New Mexico, and Wyoming. Understanding this time difference is crucial for scheduling meetings, managing customer service, and coordinating operations between Hawaii and the Mountain region.
Common Use Cases for HST to MST Conversion
Business & Work
- Scheduling calls between Hawaii offices and Mountain region headquarters
- Coordinating business operations across Hawaii and Mountain time zones
- Managing customer service and support operations
Personal & Travel
- Scheduling video calls with family and friends in Mountain states
- Planning travel between Hawaii and Mountain region cities
- Coordinating vacation and leisure activities across regions
Time Zone Information
Hawaii Standard Time (HST)
- UTC Offset: UTC-10
- IANA Timezone: Pacific/Honolulu
- Daylight Saving: No daylight saving time observed
- Major Cities: Honolulu, Hilo, Maui, Kauai, Big Island
- Coverage: State of Hawaii
Mountain Standard Time (MST)
- UTC Offset: UTC-7 (UTC-6 during MDT)
- IANA Timezone: America/Denver
- Daylight Saving: Second Sunday in March to First Sunday in November
- Major Cities: Denver, Salt Lake City, Albuquerque, Boise, Colorado Springs
- Coverage: Mountain United States and parts of Canada
Quick Reference: HST to MST
Remember: MST is always 3 hours ahead of HST, but becomes 4 hours during MDT (daylight saving time)
Frequently Asked Questions
What is the time difference between HST and MST?
Hawaii Standard Time (HST) is UTC-10, while Mountain Standard Time (MST) is UTC-7. MST is 3 hours ahead of HST. This means when it's 8:00 AM in HST, it's 11:00 AM the same day in MST.
Does Hawaii observe daylight saving time?
No, Hawaii does not observe daylight saving time. Hawaii Standard Time (HST) remains UTC-10 year-round. However, the Mountain region does observe daylight saving time, transitioning from MST (UTC-7) to MDT (UTC-6). This means the time difference varies between 3 hours (when MST is active) and 4 hours (when MDT is active).
What is the time difference during Mountain Daylight Time (MDT)?
When the Mountain region observes Mountain Daylight Time (MDT, UTC-6) from mid-March to early November, the difference becomes 4 hours. During this period, when it's 8:00 AM HST, it would be 12:00 PM (noon) MDT. This is why it's important to verify whether MST or MDT is currently active.
What major cities are in HST and MST timezones?
HST covers Hawaii cities including Honolulu, Hilo, Maui, Kauai, and the Big Island. MST covers major Mountain region cities like Denver, Salt Lake City, Albuquerque, Boise, and Colorado Springs. These regions span from Hawaii to the Mountain states.
How do I convert HST to MST manually?
To convert from HST to MST, add 3 hours to the HST time. For example, if it's 9:00 AM HST, it would be 12:00 PM (noon) MST the same day. Remember that the difference becomes 4 hours when the Mountain region observes MDT (daylight saving time).
What should I know about scheduling across HST and MST?
Hawaii is 3-4 hours behind the Mountain region, with good overlap for business coordination. Morning MST times (8-10 AM) correspond to early morning HST times (5-7 AM), while afternoon MST (2-4 PM) corresponds to late morning/early afternoon HST (11 AM-1 PM). Afternoon is generally better for scheduling as it avoids very early morning times.
Pro Tips
- • MST is always 3 hours ahead of HST - but becomes 4 hours when MDT is active (March-November).
- • Hawaii does not observe daylight saving time, so HST is consistent year-round while MST/MDT changes twice annually.
- • Afternoon Mountain times (2-4 PM MST = 11 AM-1 PM HST) work well for Hawaii-Mountain region business coordination.
- • Unlike Hawaii-East Coast coordination, Hawaii and the Mountain region have substantial daily overlap for real-time communication.
- • Use 24-hour time format when communicating across HST-MST to eliminate AM/PM confusion around early morning times.
- • Between March and November, remember the 4-hour difference when MST transitions to MDT due to daylight saving time.