Convert KST to IRST
IRST is 5 hours 30 minutes behind KST. KST is UTC+9 and IRST is UTC+3:30.
Right now: KST · IRST
Best time to schedule a meeting
Standard 9–5 working hours overlap for 2 hours: 3:00 PM–5:00 PM KST (9:00 AM–11:00 AM IRST). Schedule meetings inside that window.
| KST | IRST | Suitable? |
|---|---|---|
| 9:00 AM | 3:30 AM | outside 9–5 |
| 10:00 AM | 4:30 AM | outside 9–5 |
| 11:00 AM | 5:30 AM | outside 9–5 |
| 12:00 PM | 6:30 AM | outside 9–5 |
| 1:00 PM | 7:30 AM | outside 9–5 |
| 2:00 PM | 8:30 AM | outside 9–5 |
| 3:00 PM | 9:30 AM | working hours |
| 4:00 PM | 10:30 AM | working hours |
| 5:00 PM | 11:30 AM | working hours |
KST to IRST conversion table
| KST | IRST |
|---|---|
| 12:00 AM | 6:30 PM (previous day) |
| 1:00 AM | 7:30 PM (previous day) |
| 2:00 AM | 8:30 PM (previous day) |
| 3:00 AM | 9:30 PM (previous day) |
| 4:00 AM | 10:30 PM (previous day) |
| 5:00 AM | 11:30 PM (previous day) |
| 6:00 AM | 12:30 AM |
| 7:00 AM | 1:30 AM |
| 8:00 AM | 2:30 AM |
| 9:00 AM | 3:30 AM |
| 10:00 AM | 4:30 AM |
| 11:00 AM | 5:30 AM |
| 12:00 PM | 6:30 AM |
| 1:00 PM | 7:30 AM |
| 2:00 PM | 8:30 AM |
| 3:00 PM | 9:30 AM |
| 4:00 PM | 10:30 AM |
| 5:00 PM | 11:30 AM |
| 6:00 PM | 12:30 PM |
| 7:00 PM | 1:30 PM |
| 8:00 PM | 2:30 PM |
| 9:00 PM | 3:30 PM |
| 10:00 PM | 4:30 PM |
| 11:00 PM | 5:30 PM |
About KST
Korea Standard Time (KST) is UTC+9. It is used in South Korea, with no daylight saving.
Korea Standard Time is UTC+9, the same as Japan, and South Korea has had no daylight saving since 1988 when it was used for the Seoul Olympics. The two Koreas briefly differed: the North moved to UTC+8:30 in 2015 and returned to UTC+9 in 2018, which is the only time in modern history the peninsula ran on two clocks.
About IRST
Iran Standard Time (IRST) is UTC+3:30. It is used in Iran, all year.
Iran Standard Time is UTC+3:30. Iran ran daylight saving for decades and stopped in 2022, so material written before then puts the country half an hour further ahead in summer and is now wrong. Half-hour offsets are rare enough that scheduling tools sometimes round them, which turns a correct calculation into a thirty-minute error.
Does this gap change with the seasons?
Neither KST nor IRST shifts with the seasons, so this 5.5-hour difference holds all year. That is unusual enough to be worth relying on: most cross-continental gaps move twice a year.
This is the reason scheduling systems store an IANA zone such as Region/City rather than an offset or an abbreviation: the zone knows its own rules and the offset does not.
Frequently asked questions
What time is 9:00 AM KST in IRST?
9:00 AM KST is 3:30 AM IRST.
Is IRST ahead of KST?
IRST is 5 hours 30 minutes behind KST.
Which time zone does this use?
KST is UTC+9 and IRST is UTC+3:30. Both abbreviations denote a single fixed offset, so this conversion never shifts with daylight saving — what changes is which abbreviation a place is using at the time.