Does it account for Daylight Saving Time?

Yes, our converter uses the IANA timezone database, which includes all current DST rules for every timezone in the world.

UTC (Coordinated Universal Time) is the primary time standard by which the world regulates clocks. All timezones are defined as offsets from UTC.

Can I compare multiple timezones at once?

Yes, you can add multiple cities or timezones and see the equivalent times side by side.

How many timezones are there in the world?

There are 38 distinct UTC offsets in use, ranging from UTC-12 to UTC+14. This includes half-hour (UTC+5:30 India, UTC+9:30 Australia) and 45-minute offsets (UTC+5:45 Nepal, UTC+8:45 Australia).

What is the International Date Line?

The International Date Line (IDL) runs roughly along the 180° meridian in the Pacific Ocean. When you cross it westward, you gain a day; crossing eastward, you lose a day.

Why do some timezones have 30 or 45 minute offsets?

Countries chose offsets that best matched their solar noon. India uses UTC+5:30 and Nepal uses UTC+5:45 because standard hourly offsets didn't align well with their geography.

Which country has the most timezones?

France has the most (12 timezones) due to overseas territories. Russia spans 11 timezones. The US has 6 (including Hawaii and Alaska).

IRST to JST

+5h 30m

IRST

IRSTSOURCE

UTC+03:30

HH12

MM00

12:00 (24-hr)

12 AM6 AM12 PM6 PM12 AM

JST

UTC+09:00

HH05

MM30

17:30 (24-hr)

12 AM6 AM12 PM6 PM12 AM

Quick Reference

Time Conversion Table

IRST

JST

12:00 AM

5:30 AM

2:00 AM

7:30 AM

4:00 AM

9:30 AM

6:00 AM

11:30 AM

8:00 AM

1:30 PM

10:00 AM

3:30 PM

12:00 PM

5:30 PM

2:00 PM

7:30 PM

4:00 PM

9:30 PM

6:00 PM

11:30 PM

8:00 PM

1:30 AM+1

10:00 PM

3:30 AM+1

Green rows indicate typical business hours (9 AM - 5 PM)

IRST and JST on the World Map

The map below highlights the IRST (Iran Standard Time) and JST (Japan Standard Time) timezone regions across the globe.

IRST Zone

→

JST Zone

Explore all world timezones interactively →

IRST – Iran Standard Time

UTC+03:30

Iran Standard Time (IRST) is the time zone for Iran, 3 hours and 30 minutes ahead of UTC.

Countries in IRST

Iran

Major Cities in IRST

TehranIsfahanMashhadTabrizShirazKaraj

Key Facts about IRST

•IRST is one of only a few time zones with a 30-minute offset.
•Iran observes daylight saving time, switching to IRDT (UTC+04:30).
•Tehran has a metropolitan population of over 16 million.

Daylight Saving:Yes – switches to IRDT

Learn more about IRST on Wikipedia

JST – Japan Standard Time

UTC+09:00

Japan Standard Time (JST) is the time zone for Japan, 9 hours ahead of UTC.

Countries in JST

Japan

Major Cities in JST

TokyoOsakaYokohamaNagoyaSapporoKyotoKobeFukuokaHiroshima

Key Facts about JST

•Japan does not observe daylight saving time.
•Tokyo is the most populous metropolitan area in the world.
•The Tokyo Stock Exchange operates from 9:00 AM to 3:00 PM JST.
•JST is 14 hours ahead of EST and 9 hours ahead of GMT.

Daylight Saving:No – UTC+09:00 year-round

Learn more about JST on Wikipedia

Comparing Time Zones: IRST and JST

IRST runs on Iran Standard Time (IRST) at UTC+03:30. JST runs on Japan Standard Time (JST) at UTC+09:00. That puts IRST 5 hours 30 minutes ahead of JST — a difference of +5h 30m at the current offsets.

In practice, when it is 9:00 AM in IRST it is 2:30 PM in JST. Midnight in IRST is 5:30 AM in JST. Neither zone observes daylight saving time, so the offset between them stays constant all year.

IRST to JST time conversion table

IRST (IRST)	JST (JST)	Day
12:00 AM	5:30 AM	same day
6:00 AM	11:30 AM	same day
7:00 AM	12:30 PM	same day
8:00 AM	1:30 PM	same day
9:00 AM	2:30 PM	same day
12:00 PM	5:30 PM	same day
3:00 PM	8:30 PM	same day
5:00 PM	10:30 PM	same day
6:00 PM	11:30 PM	same day
9:00 PM	2:30 AM	next day

Why people convert IRST to JST time

Scheduling a call from IRST to JST: a 10:00 AM start in IRST lands at 3:30 PM in JST, so you can confirm the slot without doing the arithmetic yourself.
Finding shared working hours: both IRST and JST are inside the 9-to-5 working day between 9:00 AM and 11:30 AM IRST time (2:30 PM–5:00 PM JST). That is roughly 2 hours 30 minutes of usable overlap.
Coordinating a IRST-based team with JST contacts: quoting times in the other side's local clock — not your own — removes the single biggest source of missed meetings.

Always state the zone abbreviation, not just the hour. "3:00 PM IRST" is unambiguous; "3 PM" across a +5h 30m gap is not.
Block 9:00 AM–11:30 AM IRST as the recurring meeting window if you work primarily from IRST and need JST colleagues present.

About IRST (Iran Standard Time)

Iran Standard Time (IRST) is one of the few time zones with a 30-minute offset. Iran observes daylight saving time (IRDT, UTC+04:30) from late March to late September. Tehran, the capital, is one of the largest cities in the Middle East.

About JST (Japan Standard Time)

Japan Standard Time (JST) is the standard time zone for all of Japan. Japan does not observe daylight saving time. JST is 9 hours ahead of UTC and 14 hours ahead of EST. The Tokyo Stock Exchange, the world's third largest by market capitalization, operates on JST. South Korea uses the same offset (KST) but it is a distinct time zone.

Best time to call between IRST and JST

Both IRST and JST sit inside the 9 AM – 5 PM working day between 9:00 AM–11:30 AM IRST, which is 2:30 PM–5:00 PM JST. That gives roughly 2 hours and 30 minutes of shared time — the safest window for a live call or meeting.

Business hours overlap

IRST and JST overlap for about 2 hours during the working day — enough for meetings if you avoid the edges of the window.

IRST is 5 hours 30 minutes ahead of JST (IRST UTC+03:30 → JST UTC+09:00). The shared working window is 9:00 AM–11:30 AM IRST. Remember to re-check around daylight-saving transitions.

Learn More About Time

Dive deeper into the fascinating world of timekeeping, time zones, and how they shape our global society:

⏳

History of Timekeeping

From sundials to atomic clocks - 5000 years of measuring time

🌍

How Time Zones Work

UTC, offsets, and why zones don't follow straight lines

☀️

Daylight Saving Time

DST dates, which countries observe it, and the ongoing debate

Frequently Asked Questions

What is the time difference between IRST and JST?

IRST (IRST, UTC+03:30) is 5 hours 30 minutes ahead of JST (JST, UTC+09:00). The gap is currently +5h 30m.

How do I convert IRST time to JST time?

Add +5h 30m to IRST local time. For example, 9:00 AM in IRST is 2:30 PM in JST.

What time is it in JST right now?

JST uses JST at UTC+09:00. Use the live converter at the top of this page — it updates in real time and already accounts for the +5h 30m offset from IRST.