Working hours: 09:00–17:00 local. Green = both working.Purple = one side only.
Frequently Asked Questions
What is the difference between kst and ast?
Korea Standard Time (kst) is UTC+9 and Arabia Standard Time (ast) is UTC+3. The difference between them is 6 hours.
Where is kst used?
Korea Standard Time (kst) is used in South Korea and surrounding regions. The IANA timezone identifier is Asia/Seoul.
Where is ast used?
Arabia Standard Time (ast) is used in Saudi Arabia and surrounding regions. The IANA timezone identifier is Asia/Riyadh. Note: ast is ambiguous and may refer to other timezones.
How do I convert kst to ast?
Use the interactive converter above. Drag the time slider to any kst time and the ast equivalent updates instantly. You can also type a time like "3pm" or "15:00" in the input bar.
KST (Seoul) is 6 hours ahead of AST (Riyadh). Midday in KST (Seoul) lines up with 06:00 in AST (Riyadh).
KST (Seoul) observes Asia/Seoul and AST (Riyadh) observes Asia/Riyadh — a 6 hours gap between them.
Daily overlap window
There is a 2-hour window each day where both KST (Seoul) and AST (Riyadh) are within standard business hours (09:00–17:00).
00:0006:0012:0018:0024:00
KST (Seoul)
AST (Riyadh)
Overlap (2h)
Optimal meeting slots
KST (Seoul) and AST (Riyadh) share 2 hours of business hours overlap daily.
15:00 Seoul / 09:00 Riyadh✓ Both working
16:00 Seoul / 10:00 Riyadh✓ Both working
Assumes a standard 9 AM–5 PM workday in each location's local timezone.
Upcoming public holidays
KST (Seoul)7 holidays
Aug 15Liberation Day
Sep 24Chuseok
Sep 25Chuseok
Sep 26Chuseok
Oct 3National Foundation Day
AST (Riyadh)
No upcoming public holidays this year.
How to work with KST (Seoul) and AST (Riyadh) time zones
Coordinating between KST (Seoul) (South Korea) and AST (Riyadh) (Saudi Arabia) means working around a 6-hour time difference. The 2-hour overlap window gives both teams a natural slot for real-time collaboration without anyone working outside normal hours.
💡 How to schedule across these time zones
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Schedule at 15:00–16:00 (KST (Seoul)) for a 09:00–10:00 slot in AST (Riyadh) — the sweet spot where both teams are working.
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Schedule at 16:00–17:00 (KST (Seoul)) for a 10:00–11:00 slot in AST (Riyadh) — the sweet spot where both teams are working.
Recurring meetings are particularly vulnerable to DST shifts. The ClockinSync Chrome Extension alerts you before the offset changes.
Drag the slider at the top to convert any KST (Seoul) time instantly. You can also type natural language like "3pm", "15:00", or a location name to get an immediate answer.