MDT to HST Converter
Convert time between Mountain Daylight Time (MDT) and Hawaii Standard Time (HST)
Mountain Daylight Time (MDT)
Hawaii Standard Time (HST)
Time Difference
Hawaii Standard Time (HST) is 0 hours ahead of Mountain Daylight Time (MDT)
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Quick Reference
| MDT | HST |
|---|---|
| 19:00 | 16:00 |
| 21:00 | 18:00 |
| 23:00 | 20:00 |
| 01:00 | 22:00 |
| 03:00 | 00:00 |
| 05:00 | 02:00 |
| 07:00 | 04:00 |
| 09:00 | 06:00 |
| 11:00 | 08:00 |
| 13:00 | 10:00 |
| 15:00 | 12:00 |
| 17:00 | 14:00 |
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 MDT to HST Time Conversion
Converting time between Mountain Daylight Time (MDT) and Hawaii Standard Time (HST) is essential for coordinating between the US Mountain region and Hawaii during summer months (March to November). MDT is UTC-6 (daylight saving time, observed March to November), while HST is UTC-10 (year-round, Hawaii does not observe daylight saving time). MDT is consistently 4 hours ahead of HST. This is different from winter coordination when the Mountain region observes MST (UTC-7), which is only 3 hours ahead of HST.
This conversion is crucial during the summer season for businesses operating between Denver, Salt Lake City, Phoenix, and Hawaii. Tech companies, tourism operations, government agencies, and enterprises coordinating mainland mountain region and island operations rely on accurate time conversions during daylight saving season. Understanding that Hawaii Standard Time remains constant throughout the year makes scheduling easier for long-term projects spanning both seasons. The consistent 4-hour difference during MDT season (compared to the variable 3-4 hour difference when accounting for both MST and MDT) simplifies summer business operations across the mainland mountain region and islands.
Common Use Cases for MDT to HST Conversion
Business & Work
- Scheduling summer calls between Denver headquarters and Hawaii branch offices
- Coordinating business operations between Mountain region and Hawaiian locations during peak season
- Managing tourist operations and hospitality services during summer travel season
- Planning summer conference calls for companies with presence in both regions
Personal & Travel
- Coordinating with family and friends in Hawaii during summer months
- Planning summer travel between Mountain region and Hawaiian destinations
- Scheduling virtual meetings with Hawaii-based relatives during daylight hours
- Arranging online collaboration with Hawaii-based colleagues during business season
Time Zone Information
Mountain Daylight Time (MDT)
- UTC Offset: UTC-6
- IANA Timezone: America/Denver
- Daylight Saving: Daylight saving time (second Sunday in March to first Sunday in November)
- Major Cities: Denver, Salt Lake City, Albuquerque, Boise, Las Vegas
- Coverage: Mountain United States and Canada (summer months)
Hawaii Standard Time (HST)
- UTC Offset: UTC-10
- IANA Timezone: Pacific/Honolulu
- Daylight Saving: No daylight saving time (consistent year-round)
- Major Cities: Honolulu, Hilo, Kailua, Maui, Kauai
- Coverage: All Hawaiian islands (consistent year-round)
Quick Reference: MDT to HST
Remember: MDT is always 4 hours ahead of HST during daylight saving time (March-November). When daylight saving time ends (first Sunday in November) and MDT becomes MST, the difference decreases to 3 hours. Hawaii does not observe daylight saving time.
Frequently Asked Questions
What is the time difference between MDT and HST?
Mountain Daylight Time (MDT) is UTC-6, while Hawaii Standard Time (HST) is UTC-10. MDT is 4 hours ahead of HST. When it's 10:00 AM in Denver (MDT), it's 6:00 AM the same day in Honolulu (HST).
When is MDT active and how does it affect Hawaii coordination?
MDT is observed from the second Sunday in March to the first Sunday in November. During this period, the Mountain region is 4 hours ahead of Hawaii. From November to March, when the Mountain region observes MST (UTC-7), the difference is only 3 hours. This makes summer coordination (MDT season) have a larger time gap than winter coordination.
Does Hawaii observe daylight saving time like MDT does?
No, Hawaii does not observe daylight saving time. Hawaii Standard Time (HST) remains UTC-10 year-round. This is why the time difference between Hawaii and the mainland varies - the mainland changes its clocks twice per year while Hawaii stays constant. MDT is specifically the summer offset for the Mountain region.
What major cities are in MDT and HST timezones?
MDT covers major Mountain region cities including Denver, Salt Lake City, Albuquerque, Boise, and Las Vegas during summer months. HST covers all Hawaiian islands with major cities being Honolulu, Hilo, Kailua, Waihuku, and Kaneohe. These regions represent the US Mountain region during daylight saving season and the Hawaiian Islands.
What are the best times to schedule calls between MDT and HST regions?
The 4-hour difference during MDT season is significant but still manageable. Morning hours in MDT (8-10 AM) correspond to early morning in HST (4-6 AM), and late morning MDT (10 AM-12 PM) corresponds to morning HST (6-8 AM). Afternoon MDT (3-5 PM) aligns well with late morning/midday HST (11 AM-1 PM), making this an ideal window for summer business coordination.
How does summer (MDT) coordination differ from winter (MST) coordination with Hawaii?
During summer (March-November, MDT season), the Mountain region is 4 hours ahead of Hawaii, creating a larger time gap than winter. During winter (November-March, MST season), the difference is only 3 hours, providing better overlap for business hours. Many businesses adjust their summer schedules to account for the larger time difference, while winter offers more flexibility for overlapping work hours.
Pro Tips
- • MDT is always 4 hours ahead of HST during summer months (March-November).
- • When daylight saving time ends (first Sunday in November), MDT becomes MST and the difference decreases to 3 hours.
- • Early morning MDT times (8-10 AM) correspond to early morning HST times (4-6 AM), making them ideal for coordinating business operations.
- • Hawaii does not observe daylight saving time, so HST is consistent year-round while MDT changes once per season.
- • For long-term projects spanning both seasons, account for the time difference change when MDT transitions to MST in November.
- • Afternoon MDT (3-5 PM) aligns well with late morning/midday HST (11 AM-1 PM), providing excellent overlap for summer business calls and coordination.
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