HST to MDT Converter
Convert time between Hawaii Standard Time (HST) and Mountain Daylight Time (MDT)
Hawaii Standard Time (HST)
Mountain Daylight Time (MDT)
Time Difference
Mountain Daylight Time (MDT) is 0 hours ahead of Hawaii Standard Time (HST)
Select Date
Select Time
Quick Reference
| HST | MDT |
|---|---|
| 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 MDT Time Conversion
Converting time between Hawaii Standard Time (HST) and Mountain Daylight Time (MDT) is important for coordinating between Hawaii and the US Mountain region during daylight saving time. HST is UTC-10, while MDT is UTC-6, making MDT 4 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, especially during the March-November daylight saving period.
Common Use Cases for HST to MDT Conversion
Business & Work
- Scheduling calls between Hawaii offices and Mountain region headquarters during daylight saving time
- 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 during spring and summer months
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 Daylight Time (MDT)
- UTC Offset: UTC-6 (UTC-7 during MST)
- 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 MDT
Remember: MDT is always 4 hours ahead of HST during daylight saving time (March-November). Outside this period, MST is 3 hours ahead of HST
Frequently Asked Questions
What is the time difference between HST and MDT?
Hawaii Standard Time (HST) is UTC-10, while Mountain Daylight Time (MDT) is UTC-6. MDT is 4 hours ahead of HST. This means when it's 8:00 AM in HST, it's 12:00 PM (noon) the same day in MDT.
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 observes 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, November-March) and 4 hours (when MDT is active, March-November).
How does HST to MDT differ from HST to MST?
MDT (Mountain Daylight Time) is 1 hour ahead of MST (Mountain Standard Time). When MDT is active (March-November), the difference between HST and MDT is 4 hours. When MST is active (November-March), the difference between HST and MST is 3 hours. MDT is used during daylight saving time in the Mountain region.
What major cities are in HST and MDT timezones?
HST covers Hawaii cities including Honolulu, Hilo, Maui, Kauai, and the Big Island. MDT covers major Mountain region cities like Denver, Salt Lake City, Phoenix area (though Arizona doesn't observe DST), Boulder, Aspen, and other Rocky Mountain communities. These regions represent Hawaii and the Mountain West during daylight saving time (March-November).
How do I convert HST to MDT manually?
To convert from HST to MDT, add 4 hours to the HST time. For example, if it's 9:00 AM HST, it would be 1:00 PM MDT the same day. Remember this conversion is only valid during daylight saving time (March-November). When MST is active (November-March), add only 3 hours instead.
What should I know about scheduling across HST and MDT?
Hawaii is 4 hours behind the Mountain region during MDT, making coordination more challenging than with the West Coast. Morning MDT times (9-11 AM) correspond to early morning HST times (5-7 AM), and late afternoon MDT (3-5 PM) corresponds to late morning HST (11 AM-1 PM). For regular business coordination, early morning MDT calls (7-9 AM) work well with Hawaii (3-5 AM HST for early birds, or 3-5 PM HST for evening workers).
Pro Tips
- • MDT is always 4 hours ahead of HST during daylight saving time (March-November). Outside this period, MST is 3 hours ahead.
- • Hawaii does not observe daylight saving time, so HST is consistent year-round while MDT changes twice annually.
- • Afternoon MDT (2-4 PM) aligns well with late morning/early afternoon HST (10 AM-12 PM) for mid-day meetings.
- • Morning hours (7-9 AM MDT = 3-5 AM HST) work for early risers in Hawaii coordinating with Mountain region business hours.
- • Use 24-hour time format when communicating across HST-MDT to eliminate AM/PM confusion, especially around morning/evening transitions.
- • Tourism, outdoor recreation, and tech businesses between Hawaii and the Mountain region can coordinate during seasonal peaks and overlapping business hours.