JST to IRST Time Converter

When it is 9:00 AM JST, it is 3.5:00 AM IRST. Iran Standard Time (IRST, UTC+3:30) is 5.5 hours behind Japan Standard Time (JST, UTC+9). Your working-hours overlap window is 2.5:00 PM–5:00 PM JST (9:00 AM–11.5:00 AM IRST).

JST to IRST Conversion Table

Major Cities Using JST and IRST

Japan Standard Time (JST): Tokyo, Osaka, Kyoto, Yokohama.

Iran Standard Time (IRST): Tehran, Mashhad, Isfahan.

How many hours between JST and IRST?

JST is UTC+9 and IRST is UTC+3:30, a difference of 5.5 hours. IRST is behind JST. This difference can shift by an hour in either direction during Daylight Saving Time transitions — if one zone observes DST and the other doesn't, the offset narrows or widens for part of the year.

Business Hours Overlap: JST ↔ IRST

Assuming a 9:00 AM – 5:00 PM workday on each side, your working-hours overlap window is 2.5:00 pm–5:00 pm jst (9:00 am–11.5:00 am irst). To visualize this instantly for any pair of cities, use the visual meeting planner or the timezone overlap finder — both highlight the green overlap window on a live timeline.

Does JST observe Daylight Saving Time?

Japan Standard Time (JST) is based on the Asia/Tokyo IANA timezone. DST observance depends on the jurisdiction — for example, most of the continental US switches between standard and daylight time, while India, Japan, and most of Southeast Asia do not observe DST at all. WorldClock.lol uses the authoritative IANA timezone database, so every conversion automatically accounts for the correct DST rules on the date you're converting.

When is 9 AM JST in IRST?

When it is 9:00 AM in Japan Standard Time (JST, UTC+9), it is 3.5:00 AM in Iran Standard Time (IRST). For other times of day, scan the conversion table above or drop into the interactive converter to pick an exact minute. The converter handles both standard and daylight variants correctly.

How to Use This JST to IRST Converter

1. Type or drag any time in the JST input above — the IRST equivalent updates instantly.
2. Check the day indicator. When the converted time crosses midnight, the tool shows +1 day or −1 day so you don't book a meeting on the wrong date.
3. Copy the shareable URL to send the specific conversion to a colleague — the link preserves your exact selection.
4. Switch directions by swapping the input zones, or open IRST to JST for the reverse.

Related JST Converters

• JST to EST
• JST to PST
• JST to GMT
• JST to UTC
• JST to IST
• JST to CET

Related IRST Converters

• EST to IRST
• PST to IRST
• GMT to IRST
• UTC to IRST
• IST to IRST
• CET to IRST

More Time Tools

• All Time Zone Converters — browse every supported pair
• About JST (Japan Standard Time) — current time, cities, DST rules
• About IRST (Iran Standard Time) — current time, cities, DST rules
• Meeting Planner — find the best time for a multi-city meeting
• Best Time to Call — optimal calling windows between any two cities
• UTC Time Now — the reference point for every conversion
• DST Schedule 2026 — every daylight-saving transition this year