IRST to JST Time Converter

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

IRST to JST Conversion Table

Major Cities Using IRST and JST

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

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

How many hours between IRST and JST?

IRST is UTC+3:30 and JST is UTC+9, a difference of 5.5 hours. JST is ahead of IRST. 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: IRST ↔ JST

Assuming a 9:00 AM – 5:00 PM workday on each side, your working-hours overlap window is 9:00 am–11.5:00 am irst (2.5:00 pm–5:00 pm jst). 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 IRST observe Daylight Saving Time?

Iran Standard Time (IRST) is based on the Asia/Tehran 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 IRST in JST?

When it is 9:00 AM in Iran Standard Time (IRST, UTC+3:30), it is 2.5:00 PM in Japan Standard Time (JST). 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 IRST to JST Converter

1. Type or drag any time in the IRST input above — the JST 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 JST to IRST for the reverse.

Related IRST Converters

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

Related JST Converters

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

More Time Tools

• All Time Zone Converters — browse every supported pair
• About IRST (Iran Standard Time) — current time, cities, DST rules
• About JST (Japan 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