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).

Tehran to CST

-9h 30m

Tehran

IRSTSOURCE

Iran · UTC+03:30

HH12

MM00

12:00 (24-hr)

12 AM6 AM12 PM6 PM12 AM

CST

UTC-05:00☀ DST active

HH02

MM30

02:30 (24-hr)

12 AM6 AM12 PM6 PM12 AM

Quick Reference

Time Conversion Table

Tehran

CST

12:00 AM

3:30 PM-1

2:00 AM

5:30 PM-1

4:00 AM

7:30 PM-1

6:00 AM

9:30 PM-1

8:00 AM

11:30 PM-1

10:00 AM

1:30 AM

12:00 PM

3:30 AM

2:00 PM

5:30 AM

4:00 PM

7:30 AM

6:00 PM

9:30 AM

8:00 PM

11:30 AM

10:00 PM

1:30 PM

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

IRST and CST on the World Map

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

IRST Zone

→

CST 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

CST – Central Standard Time

UTC-06:00

Central Standard Time (CST) is the time zone for the central United States, Canada, and Mexico, 6 hours behind UTC.

Countries in CST

United States (Central)Canada (Manitoba, Saskatchewan)MexicoGuatemalaHondurasEl SalvadorCosta RicaNicaraguaBelize

Major Cities in CST

ChicagoHoustonDallasSan AntonioMexico CityAustinWinnipegMemphisMilwaukeeNashvilleKansas CityNew OrleansMinneapolisGuatemala City

Key Facts about CST

•CST covers 20 US states fully or partially.
•Chicago and Houston are the two largest cities in the Central Time Zone.
•Mexico City, one of the world's most populous cities, operates on CST.
•CST is 1 hour behind EST and 2 hours ahead of PST.

Daylight Saving:Yes – switches to CDT

Learn more about CST on Wikipedia

About Tehran

Wikipedia

Tehran operates on Iran Standard Time (IRST), UTC+3:30. Iran's unique half-hour offset makes Tehran time distinctive for regional business coordination.

Population:9.4 million

Metro:16.8 million

Business Hours:8:00 AM - 4:00 PM IRST

Currency:IRR (﷼)

Stock Exchange:TSE (Tehran Stock Exchange)

Key Landmarks

Azadi TowerGolestan PalaceGrand BazaarMilad TowerTabiat Bridge

Did You Know?

Iran Standard Time (IRST) is one of few timezones with a 30-minute offset (UTC+3:30).

Learn more about IRST timezone →

Tehran vs CST: Offsets, DST and Best Call Times

Tehran runs on Iran Standard Time (IRST) at UTC+03:30. CST runs on Central Standard Time (CST) at UTC-06:00. That puts Tehran 9 hours 30 minutes behind CST — a difference of -9h 30m at the current offsets.

In practice, when it is 9:00 AM in Tehran it is 11:30 PM in CST on the previous day. Midnight in Tehran is 2:30 PM in CST. Neither zone observes daylight saving time, so the offset between them stays constant all year.

Tehran to CST time conversion table

Tehran (IRST)	CST (CST)	Day
12:00 AM	2:30 PM	previous day
6:00 AM	8:30 PM	previous day
7:00 AM	9:30 PM	previous day
8:00 AM	10:30 PM	previous day
9:00 AM	11:30 PM	previous day
12:00 PM	2:30 AM	same day
3:00 PM	5:30 AM	same day
5:00 PM	7:30 AM	same day
6:00 PM	8:30 AM	same day
9:00 PM	11:30 AM	same day

Why people convert Tehran to CST time

Scheduling a call from Tehran to CST: a 10:00 AM start in Tehran lands at 12:30 AM in CST, so you can confirm the slot without doing the arithmetic yourself.
Handling a -9h 30m gap: Tehran and CST have no overlap inside a normal 9-to-5 day, so real-time meetings need an early-morning or late-evening slot on one side. 9:00 AM in CST is 11:30 PM in Tehran.
Watching a live event or market open: Tehran viewers need 11:30 PM in CST to catch a 9:00 AM start there, and 9:30 AM if the event is anchored to Tehran.

Always state the zone abbreviation, not just the hour. "3:00 PM IRST" is unambiguous; "3 PM" across a -9h 30m gap is not.
With a -9h 30m gap there is no shared 9-to-5 window, so alternate the early start: one week Tehran takes the early slot, the next week CST does.

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 CST (Central Standard Time)

Central Standard Time (CST) covers the central region of North America. It is the second most populous time zone in the US, including major cities like Chicago, Houston, and Dallas. CST is also used in Mexico City and much of Central America including Guatemala, Honduras, El Salvador, and Costa Rica. During summer, most of the US and Canada switch to Central Daylight Time (CDT, UTC-05:00), while Mexico and Central American countries generally remain on CST.

Best time to call between Tehran and CST

With a -9h 30m offset there is no overlap inside a normal 9 AM – 5 PM day. CST opens at 9:00 AM CST, which is 11:30 PM in Tehran, so real-time calls need an early-morning or late-evening slot on one side.

Business hours overlap

Tehran and CST have no shared working hours because of the -9h 30m gap. Teams need to alternate early starts or rely on asynchronous handovers.

Tehran is 9 hours 30 minutes behind CST (IRST UTC+03:30 → CST UTC-06:00). There is no shared 9-to-5 window, so plan around an early or late slot. Remember to re-check around daylight-saving transitions.

🕐 Daylight Saving Time Info

Tehran

Does not observe DST

CST

☀ Currently in DST

Standard: UTC-06:00 · DST: UTC-05:00

Clocks fall back on Sun, Nov 1, 2026

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 Tehran and CST?

Tehran (IRST, UTC+03:30) is 9 hours 30 minutes behind CST (CST, UTC-06:00). The gap is currently -9h 30m.

How do I convert Tehran time to CST time?

Add -9h 30m to Tehran local time. For example, 9:00 AM in Tehran is 11:30 PM in CST (previous day).

What time is it in CST right now?

CST uses CST at UTC-06:00. Use the live converter at the top of this page — it updates in real time and already accounts for the -9h 30m offset from Tehran.

What is the best time to call CST from Tehran?

There is no shared working-hours window because of the -9h 30m gap. The closest option is 1:00 PM in Tehran, which is 3:30 AM in CST.

Which is behind, Tehran or CST?

Tehran is 9 hours 30 minutes behind CST. When it is 12:00 PM in Tehran it is 2:30 AM in CST.

Do Tehran and CST use different time zones?

Tehran (Iran) uses IRST at UTC+03:30, while CST uses CST at UTC-06:00. The IANA identifiers are Asia/Tehran and America/Chicago.

Does daylight saving time affect the Tehran–CST difference?

Neither zone observes daylight saving time, so the -9h 30m offset between Tehran and CST is fixed all year.

Which other cities share Tehran's time zone?

IRST also covers Tehran, Isfahan, Mashhad, Tabriz, Shiraz, Karaj.

Which countries use IRST, Tehran's zone?

IRST is used in Iran.

Is there a day difference between Tehran and CST?

Not normally. The -9h 30m gap only pushes the date over the previous day.

What is the time difference between Tehran and CST?

CST is -9h 30m from Tehran.

What timezone is Tehran in?

Tehran operates on Iran Standard Time (IRST), UTC+3:30. Iran's unique half-hour offset makes Tehran time distinctive for regional business coordination.