IRST to HST
-13h 30mIRST
IRSTSOURCEHST
HSTGreen rows indicate typical business hours (9 AM - 5 PM)
IRST and HST on the World Map
The map below highlights the IRST (Iran Standard Time) and HST (Hawaii Standard Time) timezone regions across the globe.
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.
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).
Everything You Need to Know About IRST and HST Time
IRST runs on Iran Standard Time (IRST) at UTC+03:30. HST runs on Hawaii Standard Time (HST) at UTC-10:00. That puts IRST 13 hours 30 minutes behind HST — a difference of -13h 30m at the current offsets.
In practice, when it is 9:00 AM in IRST it is 7:30 PM in HST on the previous day. Midnight in IRST is 10:30 AM in HST. Neither zone observes daylight saving time, so the offset between them stays constant all year.
IRST to HST time conversion table
| IRST (IRST) | HST (HST) | Day |
|---|---|---|
| 12:00 AM | 10:30 AM | previous day |
| 6:00 AM | 4:30 PM | previous day |
| 7:00 AM | 5:30 PM | previous day |
| 8:00 AM | 6:30 PM | previous day |
| 9:00 AM | 7:30 PM | previous day |
| 12:00 PM | 10:30 PM | previous day |
| 3:00 PM | 1:30 AM | same day |
| 5:00 PM | 3:30 AM | same day |
| 6:00 PM | 4:30 AM | same day |
| 9:00 PM | 7:30 AM | same day |
Why people convert IRST to HST time
- Scheduling a call from IRST to HST: a 10:00 AM start in IRST lands at 8:30 PM in HST the previous day, so you can confirm the slot without doing the arithmetic yourself.
- Handling a -13h 30m gap: IRST and HST 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 HST is 7:30 PM in IRST.
- Coordinating a IRST-based team with HST contacts: quoting times in the other side's local clock — not your own — removes the single biggest source of missed meetings.
- Always state the zone abbreviation, not just the hour. "3:00 PM IRST" 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 IRST takes the early slot, the next week HST does.
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.
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.
Best time to call between IRST and HST
With a -13h 30m offset there is no overlap inside a normal 9 AM – 5 PM day. HST opens at 9:00 AM HST, which is 7:30 PM in IRST, so real-time calls need an early-morning or late-evening slot on one side.
Business hours overlap
IRST and HST have no shared working hours because of the -13h 30m gap. Teams need to alternate early starts or rely on asynchronous handovers.
IRST is 13 hours 30 minutes behind HST (IRST UTC+03:30 → HST UTC-10:00). 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 IRST and HST?
IRST (IRST, UTC+03:30) is 13 hours 30 minutes behind HST (HST, UTC-10:00). The gap is currently -13h 30m.
How do I convert IRST time to HST time?
Add -13h 30m to IRST local time. For example, 9:00 AM in IRST is 7:30 PM in HST (previous day).
What time is it in HST right now?
HST uses HST at UTC-10:00. Use the live converter at the top of this page — it updates in real time and already accounts for the -13h 30m offset from IRST.
What is the best time to call HST from IRST?
There is no shared working-hours window because of the -13h 30m gap. The closest option is 1:00 PM in IRST, which is 11:30 PM in HST.
Which is behind, IRST or HST?
IRST is 13 hours 30 minutes behind HST. When it is 12:00 PM in IRST it is 10:30 PM in HST.
Does daylight saving time affect the IRST–HST difference?
Neither zone observes daylight saving time, so the -13h 30m offset between IRST and HST is fixed all year.
Which other cities share IRST's time zone?
IRST also covers Tehran, Isfahan, Mashhad, Tabriz, Shiraz, Karaj.
Which countries use IRST, IRST's zone?
IRST is used in Iran.
Is there a day difference between IRST and HST?
Sometimes. The -13h 30m gap is large enough that 8:00 PM or later in IRST already falls on the in HST.
What is the time difference between IRST and HST?
HST is -13h 30m from IRST.
What timezone is IRST in?
IRST operates on its local timezone.
What timezone is HST in?
HST operates on its local timezone.
Which countries use IRST (Iran Standard Time)?
IRST is used in Iran.
Does IRST observe daylight saving time?
Yes, IRST switches to IRDT during summer months.
What are some interesting facts about IRST?
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).
Which cities are in the HST timezone?
Major cities in the HST timezone include Honolulu, Hilo, Kailua, Pearl City, Kapolei.
What is the UTC offset for HST?
Hawaii Standard Time (HST) is at UTC-10:00.
What should I know about the HST timezone?
Hawaii does not observe daylight saving time. HST is 5 hours behind EST in winter and 6 hours behind EDT in summer.
When is it midnight in IRST, what time is it in HST?
When it is 12:00 AM (midnight) in IRST (IRST), it is -13h 30m later in HST (HST).
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