What is the time difference between IRST and JST?

Japan Standard Time (JST) is 5 hours and 30 minutes ahead of Iran Standard Time (IRST). IRST uses a UTC offset of UTC+3:30, while JST uses UTC+9. For example, when it's 9:00 AM in IRST, it's 2:30 PM in JST. 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 IRST to JST?

To convert IRST to JST, add 5 hours and 30 minutes to the IRST time. For example, 9:00 AM IRST is 2:30 PM JST, and 5:00 PM IRST is 10:30 PM JST. 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 JST when it's noon in IRST?

When it's 12:00 PM (noon) in IRST, it's 5:30 PM in JST. This is because JST is 5 hours and 30 minutes ahead of IRST. Similarly, when it's 6:00 PM in IRST, it's 11:30 PM in JST. This relationship is constant throughout the year. The color-coded conversion table above shows every hour mapped between both timezones.

How many hours ahead is JST from IRST?

JST is 5 hours and 30 minutes ahead of IRST. This means when it's 9:00 AM in IRST, it's 2:30 PM in JST, and when it's midnight in IRST, it's 5:30 AM in JST. 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 JST ahead or behind IRST?

JST is ahead of IRST by 5 hours and 30 minutes. Clocks in JST show a later time than IRST, meaning the day starts earlier in JST relative to IRST. For example, when it's morning in IRST, it's later in the morning in JST. This difference stays the same year-round.

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.

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 to JST more predictable. Countries and regions in this timezone keep their clocks unchanged regardless of the season.

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

The best time for a call between IRST and JST is during overlapping business hours (9 AM – 5 PM) in both timezones. To reach someone in JST during their work day, call between 3:30 AM and 11:30 AM your IRST time. Avoid calling too early or late, as the 5 hours and 30 minutes difference means your evening could be their late night. Check the color-coded conversion table above — green hours indicate business hours in both zones, making it easy to find the ideal time.

Do IRST and JST ever have the same time?

No, IRST and JST 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.

IRST to JST Converter

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

Timezone Details

Tehran

10:23 AM

Saturday, April 4, 2026

Tehran (UTC+03:30)

Japan Standard Time

3:53 PM

Saturday, April 4, 2026

JST (UTC+09:00)

Difference: +5h 30m

JST DST: No

24-Hour Overview

Tehran — 24-hour overview

12a12a

3a3a

6a6a

9a9a

10a

11a

12p12p

3p3p

6p6p

9p9p

10p

11p

NightMorningBusinessEvening

JST — 24-hour overview

5a5a

8a8a

10a

11a11a

12p

2p2p

5p5p

8p8p

10p

11p11p

12a

2a2a

NightMorningBusinessEvening

Frequently Asked Questions

Related Conversions

JST to IRST 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

IRST Cities

Tehran

JST Cities

Tokyo Osaka Fukuoka

More Tools

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

Learn More

How Time Zones Work Understanding DST Timezone Abbreviations

External Resources

Japan Standard Time on Wikipedia IANA Time Zone Database