What is the time difference between JST and IRST?

Iran Standard Time (IRST) is 5 hours and 30 minutes behind Japan Standard Time (JST). JST uses a UTC offset of UTC+9, while IRST uses UTC+3:30. For example, when it's 9:00 AM in JST, it's 3:30 AM in IRST. This difference remains constant year-round since neither timezone observes daylight saving time. Use the conversion table above to see the exact time for each hour of the day.

How do I convert JST to IRST?

To convert JST to IRST, subtract 5 hours and 30 minutes from the JST time. For example, 9:00 AM JST is 3:30 AM IRST, and 5:00 PM JST is 11:30 AM IRST. Since neither timezone observes DST, this conversion stays the same all year. You can also use the interactive converter above for quick, accurate results.

What time is it in IRST when it's noon in JST?

When it's 12:00 PM (noon) in JST, it's 6:30 AM in IRST. This is because IRST is 5 hours and 30 minutes behind JST. Similarly, when it's 6:00 PM in JST, it's 12:30 PM in IRST. This relationship is constant throughout the year. The color-coded conversion table above shows every hour mapped between both timezones.

How many hours behind is IRST from JST?

IRST is 5 hours and 30 minutes behind JST. This means when it's 9:00 AM in JST, it's 3:30 AM in IRST, and when it's midnight in JST, it's 6:30 PM in IRST. This offset is constant throughout the year since neither timezone uses daylight saving time. The conversion table above provides a complete hour-by-hour mapping.

Is IRST ahead or behind JST?

IRST is behind JST by 5 hours and 30 minutes. Clocks in IRST show an earlier time than JST, meaning the day starts later in IRST relative to JST. For example, when it's noon in JST, it's still 6:30 AM in IRST. This difference stays the same year-round.

Does JST observe daylight saving time?

No, Japan Standard Time does not observe daylight saving time. The UTC offset of UTC+9 remains the same year-round, making time conversions from JST more predictable. Countries and regions in this timezone keep their clocks unchanged regardless of the season.

Does IRST observe daylight saving time?

No, Iran Standard Time does not observe daylight saving time. The UTC offset of UTC+3:30 remains the same year-round, which simplifies time conversions. Regions using IRST keep their clocks unchanged regardless of the season.

What is the best time to call from JST to IRST?

The best time for a call between JST and IRST is during overlapping business hours (9 AM – 5 PM) in both timezones. To reach someone in IRST during their work day, call between 2:30 PM and 10:30 PM your JST time. Avoid calling too early or late, as the 5 hours and 30 minutes difference means your evening could be their early morning. Check the color-coded conversion table above — green hours indicate business hours in both zones, making it easy to find the ideal time.

Do JST and IRST ever have the same time?

No, JST and IRST are always 5 hours and 30 minutes apart and never display the same clock time simultaneously. Neither timezone observes DST, so the difference is constant year-round with no seasonal variation. The 5 hours and 30 minutes offset is determined by their fixed positions relative to the Prime Meridian (UTC). You can always rely on this consistent difference when planning across these timezones.

JST to IRST Converter

Convert Japan Standard Time to Iran Standard Time. See the hour-by-hour conversion table below.

Timezone Details

Japan Standard Time

10:20 AM

Tuesday, June 9, 2026

JST (UTC+09:00)

Tehran

4:50 AM

Tuesday, June 9, 2026

Tehran (UTC+03:30)

Difference: -5h 30m

JST DST: No

24-Hour Overview

JST — 24-hour overview

12a12a

3a3a

6a6a

9a9a

10a

11a

12p12p

3p3p

6p6p

9p9p

10p

11p

NightMorningBusinessEvening

Tehran — 24-hour overview

6p6p

9p9p

10p

11p

12a12a

3a3a

6a6a

9a9a

10a

11a

12p12p

3p3p

NightMorningBusinessEvening

Frequently Asked Questions

Related Conversions

IRST to JST EST to JST JST to EST PST to JST JST to PST GMT to JST JST to GMT IST to JST JST to IST

Cities in These Timezones

JST Cities

Tokyo Osaka Fukuoka

IRST Cities

Tehran

More Tools

Compare JST & IRST Plan a Meeting (JST & IRST)See on Map

Learn More

How Time Zones Work Understanding DST Timezone Abbreviations

External Resources

Japan Standard Time on Wikipedia IANA Time Zone Database