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 Chicago

-8h 30m

Tehran

IRSTSOURCE

Iran · UTC+03:30

HH12

MM00

12:00 (24-hr)

12 AM6 AM12 PM6 PM12 AM

Chicago

CDT

USA · UTC-05:00☀ DST active

HH03

MM30

03:30 (24-hr)

12 AM6 AM12 PM6 PM12 AM

Quick Reference

Time Conversion Table

Tehran

Chicago

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 CDT on the World Map

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

IRST Zone

→

CDT 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 →

About Chicago

Wikipedia

Chicago operates on Central Time (CST/CDT), 1 hour behind New York. Home to CME and CBOE, Chicago is a global center for derivatives trading.

Population:2.7 million

Metro:9.5 million

Business Hours:8:00 AM - 5:00 PM CST

Currency:USD ($)

Stock Exchange:CME (Chicago Mercantile Exchange), CBOE

Key Landmarks

Willis TowerMillennium ParkCloud Gate (The Bean)Navy PierArt Institute of Chicago

Did You Know?

The Chicago Board of Trade is the world's oldest futures and options exchange.

Learn more about CDT timezone →

Tehran vs Chicago: Offsets, DST and Best Call Times

Tehran runs on Iran Standard Time (IRST) at UTC+03:30. Chicago runs on Central Daylight Time (CDT) at UTC-05:00, also currently on daylight saving time. That puts Tehran 8 hours 30 minutes behind Chicago — a difference of -8h 30m at the current offsets.

In practice, when it is 9:00 AM in Tehran it is 12:30 AM in Chicago. Midnight in Tehran is 3:30 PM in Chicago.Chicago observes daylight saving time while Tehran does not, so the gap narrows or widens by an hour part of the year.

Tehran to Chicago time conversion table

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

Why people convert Tehran to Chicago time

Scheduling a call from Tehran to Chicago: a 10:00 AM start in Tehran lands at 1:30 AM in Chicago, so you can confirm the slot without doing the arithmetic yourself.
Handling a -8h 30m gap: Tehran and Chicago 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 Chicago is 12:30 AM in Tehran.
Watching a live event or market open: Tehran viewers need 12:30 AM in Chicago to catch a 9:00 AM start there, and 8:30 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 -8h 30m gap is not.
With a -8h 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 Chicago does.
Chicago: Clocks fall back on Sun, Nov 1, 2026. Any meeting series spanning that date will shift by an hour in local time.

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 Chicago

With a -8h 30m offset there is no overlap inside a normal 9 AM – 5 PM day. Chicago opens at 9:00 AM CDT, which is 12:30 AM in Tehran, so real-time calls need an early-morning or late-evening slot on one side.

Business hours overlap

Tehran and Chicago have no shared working hours because of the -8h 30m gap. Teams need to alternate early starts or rely on asynchronous handovers.

Tehran is 8 hours 30 minutes behind Chicago (IRST UTC+03:30 → CDT UTC-05:00). 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

Chicago

☀ 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 Chicago?

Tehran (IRST, UTC+03:30) is 8 hours 30 minutes behind Chicago (CDT, UTC-05:00). The gap is currently -8h 30m.

How do I convert Tehran time to Chicago time?

Add -8h 30m to Tehran local time. For example, 9:00 AM in Tehran is 12:30 AM in Chicago.

What time is it in Chicago right now?

Chicago uses CDT at UTC-05:00. Use the live converter at the top of this page — it updates in real time and already accounts for the -8h 30m offset from Tehran.

What is the best time to call Chicago from Tehran?

There is no shared working-hours window because of the -8h 30m gap. The closest option is 1:00 PM in Tehran, which is 4:30 AM in Chicago.

Which is behind, Tehran or Chicago?

Tehran is 8 hours 30 minutes behind Chicago. When it is 12:00 PM in Tehran it is 3:30 AM in Chicago.

Do Tehran and Chicago use different time zones?

Tehran (Iran) uses IRST at UTC+03:30, while Chicago (USA) uses CDT at UTC-05:00. The IANA identifiers are Asia/Tehran and America/Chicago.

Does daylight saving time affect the Tehran–Chicago difference?

Yes at the moment: Chicago is on daylight saving time and Tehran is not, so the -8h 30m gap shifts by an hour when exactly one of them changes clocks.

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 Chicago?

Not normally. The -8h 30m gap only pushes the date over the previous day.

What is the time difference between Tehran and Chicago?

Chicago is -8h 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.

What timezone is Chicago in?

Chicago operates on Central Time (CST/CDT), 1 hour behind New York. Home to CME and CBOE, Chicago is a global center for derivatives trading.

What are the business hours in Tehran?

Standard business hours in Tehran are 8:00 AM - 4:00 PM IRST.

What are the business hours in Chicago?

Standard business hours in Chicago are 8:00 AM - 5:00 PM CST.

What is the best time to schedule a call between Tehran and Chicago?

The best overlap for a call is when both cities are in business hours. Tehran works 8:00 AM - 4:00 PM IRST and Chicago works 8:00 AM - 5:00 PM CST (-8h 30m difference). Try scheduling during the overlapping window for maximum convenience.

What currencies are used in Tehran and Chicago?

Tehran uses IRR (﷼) while Chicago uses USD ($). Check current exchange rates when planning travel or business between these cities.

How do Tehran and Chicago compare in size?

Tehran has a population of approximately 9.4 million (metro: 16.8 million), while Chicago has approximately 2.7 million (metro: 9.5 million).

What are the major landmarks in Tehran and Chicago?

Tehran is known for Azadi Tower, Golestan Palace, Grand Bazaar. Chicago is famous for Willis Tower, Millennium Park, Cloud Gate (The Bean).

Do Tehran and Chicago have stock exchanges?

Yes. Tehran has the TSE (Tehran Stock Exchange) and Chicago has the CME (Chicago Mercantile Exchange), CBOE. The -8h 30m time difference affects trading hour overlaps between these exchanges.