HST to Tehran
+13h 30mHST
HSTSOURCETehran
IRSTGreen rows indicate typical business hours (9 AM - 5 PM)
HST and IRST on the World Map
The map below highlights the HST (Hawaii Standard Time) and IRST (Iran 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).
IRST – Iran Standard Time
UTC+03:30Iran Standard Time (IRST) is the time zone for Iran, 3 hours and 30 minutes ahead of UTC.
- •IRST is one of only a few time zones with a 30-minute offset.
- •Iran observes daylight saving time, switching to IRDT (UTC+04:30).
- •Tehran has a metropolitan population of over 16 million.
About Tehran
WikipediaTehran operates on Iran Standard Time (IRST), UTC+3:30. Iran's unique half-hour offset makes Tehran time distinctive for regional business coordination.
Iran Standard Time (IRST) is one of few timezones with a 30-minute offset (UTC+3:30).
Comparing Time Zones: HST and Tehran
HST runs on Hawaii Standard Time (HST) at UTC-10:00. Tehran runs on Iran Standard Time (IRST) at UTC+03:30. That puts HST 13 hours 30 minutes ahead of Tehran — a difference of +13h 30m at the current offsets.
In practice, when it is 9:00 AM in HST it is 10:30 PM in Tehran. Midnight in HST is 1:30 PM in Tehran. Neither zone observes daylight saving time, so the offset between them stays constant all year.
HST to Tehran time conversion table
| HST (HST) | Tehran (IRST) | Day |
|---|---|---|
| 12:00 AM | 1:30 PM | same day |
| 6:00 AM | 7:30 PM | same day |
| 7:00 AM | 8:30 PM | same day |
| 8:00 AM | 9:30 PM | same day |
| 9:00 AM | 10:30 PM | same day |
| 12:00 PM | 1:30 AM | next day |
| 3:00 PM | 4:30 AM | next day |
| 5:00 PM | 6:30 AM | next day |
| 6:00 PM | 7:30 AM | next day |
| 9:00 PM | 10:30 AM | next day |
Why people convert HST to Tehran time
- Scheduling a call from HST to Tehran: a 10:00 AM start in HST lands at 11:30 PM in Tehran, so you can confirm the slot without doing the arithmetic yourself.
- Handling a +13h 30m gap: HST and Tehran have no overlap inside a normal 9-to-5 day, so real-time meetings need an early-morning or late-evening slot on one side. 9:00 AM in Tehran is 10:30 PM in HST.
- Keeping family and friends in sync: knowing that 8:00 PM in HST is 9:30 AM in Tehran 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 +13h 30m gap is not.
- With a +13h 30m gap there is no shared 9-to-5 window, so alternate the early start: one week HST takes the early slot, the next week Tehran does.
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 IRST (Iran Standard Time)
Iran Standard Time (IRST) is one of the few time zones with a 30-minute offset. Iran observes daylight saving time (IRDT, UTC+04:30) from late March to late September. Tehran, the capital, is one of the largest cities in the Middle East.
Best time to call between HST and Tehran
With a +13h 30m offset there is no overlap inside a normal 9 AM – 5 PM day. Tehran opens at 9:00 AM IRST, which is 10:30 PM in HST, so real-time calls need an early-morning or late-evening slot on one side.
Business hours overlap
HST and Tehran have no shared working hours because of the +13h 30m gap. Teams need to alternate early starts or rely on asynchronous handovers.
HST is 13 hours 30 minutes ahead of Tehran (HST UTC-10:00 → IRST UTC+03:30). There is no shared 9-to-5 window, so plan around an early or late slot. Remember to re-check around daylight-saving transitions.
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 Tehran?
HST (HST, UTC-10:00) is 13 hours 30 minutes ahead of Tehran (IRST, UTC+03:30). The gap is currently +13h 30m.
How do I convert HST time to Tehran time?
Add +13h 30m to HST local time. For example, 9:00 AM in HST is 10:30 PM in Tehran.
What time is it in Tehran right now?
Tehran uses IRST at UTC+03:30. Use the live converter at the top of this page — it updates in real time and already accounts for the +13h 30m offset from HST.
What is the best time to call Tehran from HST?
There is no shared working-hours window because of the +13h 30m gap. The closest option is 1:00 PM in HST, which is 2:30 AM in Tehran.
Which is ahead, HST or Tehran?
HST is 13 hours 30 minutes ahead of Tehran. When it is 12:00 PM in HST it is 1:30 AM in Tehran.
Do HST and Tehran use different time zones?
HST uses HST at UTC-10:00, while Tehran (Iran) uses IRST at UTC+03:30. The IANA identifiers are Pacific/Honolulu and Asia/Tehran.
Does daylight saving time affect the HST–Tehran difference?
Neither zone observes daylight saving time, so the +13h 30m offset between HST and Tehran 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 Tehran?
Sometimes. The +13h 30m gap is large enough that 8:00 PM or later in HST already falls on the next day in Tehran.
What is the time difference between HST and Tehran?
Tehran is +13h 30m from HST.
What timezone is HST in?
HST operates on its local timezone.
What timezone is Tehran in?
Tehran operates on Iran Standard Time (IRST), UTC+3:30. Iran's unique half-hour offset makes Tehran time distinctive for regional business coordination.
What are the business hours in Tehran?
Standard business hours in Tehran are 8:00 AM - 4:00 PM IRST.
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 IRST timezone?
Major cities in the IRST timezone include Tehran, Isfahan, Mashhad, Tabriz, Shiraz, Karaj.
What is the UTC offset for IRST?
Iran Standard Time (IRST) is at UTC+03:30. During daylight saving time, it shifts to IRDT.
What should I know about the IRST timezone?
IRST is one of only a few time zones with a 30-minute offset. Iran observes daylight saving time, switching to IRDT (UTC+04:30).
When is it midnight in HST, what time is it in Tehran?
When it is 12:00 AM (midnight) in HST (HST), it is +13h 30m later in Tehran (IRST).
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