South Korea to IRST
-5h 30mSouth Korea
KSTSOURCEIRST
IRSTGreen rows indicate typical business hours (9 AM - 5 PM)
KST and IRST on the World Map
The map below highlights the KST (Korea Standard Time) and IRST (Iran Standard Time) timezone regions across the globe.
KST – Korea Standard Time
UTC+09:00Korea Standard Time (KST) is the time zone for South Korea, 9 hours ahead of UTC.
- •South Korea does not observe daylight saving time.
- •Seoul is home to Samsung, LG, and Hyundai headquarters.
- •KST is the same offset as JST (UTC+09:00).
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.
Understanding the -5h 30m Gap: South Korea vs IRST
South Korea runs on Korean Standard Time (KST) at UTC+09:00. IRST runs on Iran Standard Time (IRST) at UTC+03:30. That puts South Korea 5 hours 30 minutes behind IRST — a difference of -5h 30m at the current offsets.
In practice, when it is 9:00 AM in South Korea it is 3:30 AM in IRST. Midnight in South Korea is 6:30 PM in IRST. Neither zone observes daylight saving time, so the offset between them stays constant all year.
South Korea to IRST time conversion table
| South Korea (KST) | IRST (IRST) | Day |
|---|---|---|
| 12:00 AM | 6:30 PM | previous day |
| 6:00 AM | 12:30 AM | same day |
| 7:00 AM | 1:30 AM | same day |
| 8:00 AM | 2:30 AM | same day |
| 9:00 AM | 3:30 AM | same day |
| 12:00 PM | 6:30 AM | same day |
| 3:00 PM | 9:30 AM | same day |
| 5:00 PM | 11:30 AM | same day |
| 6:00 PM | 12:30 PM | same day |
| 9:00 PM | 3:30 PM | same day |
Why people convert South Korea to IRST time
- Scheduling a call from South Korea to IRST: a 10:00 AM start in South Korea lands at 4:30 AM in IRST, so you can confirm the slot without doing the arithmetic yourself.
- Finding shared working hours: both South Korea and IRST are inside the 9-to-5 working day between 2:30 PM and 5:00 PM KST time (9:00 AM–11:30 AM IRST). That is roughly 2 hours 30 minutes of usable overlap.
- Watching a live event or market open: South Korea viewers need 3:30 AM in IRST to catch a 9:00 AM start there, and 5:30 AM if the event is anchored to South Korea.
- Always state the zone abbreviation, not just the hour. "3:00 PM KST" is unambiguous; "3 PM" across a -5h 30m gap is not.
- Block 2:30 PM–5:00 PM KST as the recurring meeting window if you work primarily from South Korea and need IRST colleagues present.
About KST (Korea Standard Time)
Korea Standard Time (KST) is the time zone used in South Korea. It shares the same UTC offset as Japan Standard Time but is a distinct time zone. South Korea does not observe daylight saving time. Seoul, the capital, is a major global tech and business hub.
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 South Korea and IRST
Both South Korea and IRST sit inside the 9 AM – 5 PM working day between 2:30 PM–5:00 PM KST, which is 9:00 AM–11:30 AM IRST. That gives roughly 2 hours and 30 minutes of shared time — the safest window for a live call or meeting.
Business hours overlap
South Korea and IRST overlap for about 2 hours during the working day — enough for meetings if you avoid the edges of the window.
South Korea is 5 hours 30 minutes behind IRST (KST UTC+09:00 → IRST UTC+03:30). The shared working window is 2:30 PM–5:00 PM KST. 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 South Korea and IRST?
South Korea (KST, UTC+09:00) is 5 hours 30 minutes behind IRST (IRST, UTC+03:30). The gap is currently -5h 30m.
How do I convert South Korea time to IRST time?
Add -5h 30m to South Korea local time. For example, 9:00 AM in South Korea is 3:30 AM in IRST.
What time is it in IRST right now?
IRST 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 -5h 30m offset from South Korea.
What is the best time to call IRST from South Korea?
Call between 2:30 PM and 5:00 PM KST — that maps to 9:00 AM–11:30 AM IRST and keeps both parties inside the working day.
Which is behind, South Korea or IRST?
South Korea is 5 hours 30 minutes behind IRST. When it is 12:00 PM in South Korea it is 6:30 AM in IRST.
Do South Korea and IRST use different time zones?
South Korea (South Korea) uses KST at UTC+09:00, while IRST uses IRST at UTC+03:30. The IANA identifiers are Asia/Seoul and Asia/Tehran.
Does daylight saving time affect the South Korea–IRST difference?
Neither zone observes daylight saving time, so the -5h 30m offset between South Korea and IRST is fixed all year.
Which other cities share South Korea's time zone?
KST also covers Seoul, Busan, Incheon, Daegu, Daejeon, Pyongyang.
Which countries use KST, South Korea's zone?
KST is used in South Korea, North Korea.
Is there a day difference between South Korea and IRST?
Not normally. The -5h 30m gap only pushes the date over the previous day.
What is the time difference between South Korea and IRST?
IRST is -5h 30m from South Korea.
What timezone is South Korea in?
South Korea operates on its local timezone.
What timezone is IRST in?
IRST operates on its local timezone.
Which countries use KST (Korea Standard Time)?
KST is used in South Korea, North Korea.
Does KST observe daylight saving time?
No, KST does not observe daylight saving time and remains at UTC+09:00 year-round.
What are some interesting facts about KST?
South Korea does not observe daylight saving time. Seoul is home to Samsung, LG, and Hyundai headquarters.
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 South Korea, what time is it in IRST?
When it is 12:00 AM (midnight) in South Korea (KST), it is -5h 30m later in IRST (IRST).
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