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).

Denver to Tehran

+9h 30m

Denver

MDTSOURCE

USA · UTC-06:00☀ DST active

HH12

MM00

12:00 (24-hr)

12 AM6 AM12 PM6 PM12 AM

Tehran

IRST

Iran · UTC+03:30

HH09

MM30

21:30 (24-hr)

12 AM6 AM12 PM6 PM12 AM

Quick Reference

Time Conversion Table

Denver

Tehran

12:00 AM

9:30 AM

2:00 AM

11:30 AM

4:00 AM

1:30 PM

6:00 AM

3:30 PM

8:00 AM

5:30 PM

10:00 AM

7:30 PM

12:00 PM

9:30 PM

2:00 PM

11:30 PM

4:00 PM

1:30 AM+1

6:00 PM

3:30 AM+1

8:00 PM

5:30 AM+1

10:00 PM

7:30 AM+1

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

MDT and IRST on the World Map

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

MDT Zone

→

IRST Zone

Explore all world timezones interactively →

MST – Mountain Standard Time

UTC-07:00

Mountain Standard Time (MST) is the time zone for the Mountain region of North America, 7 hours behind UTC.

Countries in MST

United States (Mountain)Canada (Alberta)Mexico (Chihuahua, Sonora)

Major Cities in MST

DenverPhoenixSalt Lake CityCalgaryEdmontonAlbuquerqueEl PasoTucsonBoiseCiudad Juárez

Key Facts about MST

•Arizona does not observe daylight saving time, staying on MST year-round.
•The Navajo Nation in Arizona does observe DST, unlike the rest of the state.
•Denver, the 'Mile High City', is the largest city fully in MST.
•MST covers 6 US states entirely and parts of several others.

Daylight Saving:Yes – switches to MDT

Learn more about MST on Wikipedia

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

About Denver

Wikipedia

Denver operates on Mountain Time (MST/MDT), 2 hours behind New York. As a tech and aerospace hub, Denver bridges West Coast and Central US business hours.

Population:715,000

Metro:2.9 million

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

Currency:USD ($)

Key Landmarks

Red Rocks AmphitheatreDenver Art MuseumUnion Station16th Street MallColorado State Capitol

Did You Know?

Denver International Airport is the largest airport in North America by land area.

Learn more about MDT timezone →

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 →

Denver vs Tehran: Offsets, DST and Best Call Times

Denver runs on Mountain Daylight Time (MDT) at UTC-06:00, currently observing daylight saving time. Tehran runs on Iran Standard Time (IRST) at UTC+03:30. That puts Denver 9 hours 30 minutes ahead of Tehran — a difference of +9h 30m at the current offsets.

In practice, when it is 9:00 AM in Denver it is 6:30 PM in Tehran. Midnight in Denver is 9:30 AM in Tehran.Denver observes daylight saving time while Tehran does not, so the gap narrows or widens by an hour part of the year.

Denver to Tehran time conversion table

Denver (MDT)	Tehran (IRST)	Day
12:00 AM	9:30 AM	same day
6:00 AM	3:30 PM	same day
7:00 AM	4:30 PM	same day
8:00 AM	5:30 PM	same day
9:00 AM	6:30 PM	same day
12:00 PM	9:30 PM	same day
3:00 PM	12:30 AM	next day
5:00 PM	2:30 AM	next day
6:00 PM	3:30 AM	next day
9:00 PM	6:30 AM	next day

Why people convert Denver to Tehran time

Scheduling a call from Denver to Tehran: a 10:00 AM start in Denver lands at 7:30 PM in Tehran, so you can confirm the slot without doing the arithmetic yourself.
Handling a +9h 30m gap: Denver and Tehran 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 Tehran is 6:30 PM in Denver.
Booking travel or deliveries: tracking Tehran local time against Denver keeps pickup windows and arrival estimates honest across the +9h 30m offset.

Always state the zone abbreviation, not just the hour. "3:00 PM MDT" 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 Denver takes the early slot, the next week Tehran does.
Denver: Clocks fall back on Sun, Nov 1, 2026. Re-check this page after that date because the offset changes and so does the +9h 30m gap.

About MST (Mountain Standard Time)

Mountain Standard Time (MST) covers the Rocky Mountain region of the United States and Canada. Arizona is notable for not observing daylight saving time, staying on MST year-round (except the Navajo Nation). The time zone includes major cities like Denver, Phoenix, Calgary, and Salt Lake City. During summer, most areas switch to Mountain Daylight Time (MDT, UTC-06:00).

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.

Best time to call between Denver and Tehran

With a +9h 30m offset there is no overlap inside a normal 9 AM – 5 PM day. Tehran opens at 9:00 AM IRST, which is 6:30 PM in Denver, so real-time calls need an early-morning or late-evening slot on one side.

Business hours overlap

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

Denver is 9 hours 30 minutes ahead of Tehran (MDT UTC-06:00 → IRST UTC+03:30). 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

Denver

☀ Currently in DST

Standard: UTC-07:00 · DST: UTC-06:00

Clocks fall back on Sun, Nov 1, 2026

Tehran

Does not observe DST

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 Denver and Tehran?

Denver (MDT, UTC-06:00) is 9 hours 30 minutes ahead of Tehran (IRST, UTC+03:30). The gap is currently +9h 30m.

How do I convert Denver time to Tehran time?

Add +9h 30m to Denver local time. For example, 9:00 AM in Denver is 6:30 PM in Tehran.

What time is it in Tehran right now?

Tehran uses IRST at UTC+03:30. Use the live converter at the top of this page — it updates in real time and already accounts for the +9h 30m offset from Denver.

What is the best time to call Tehran from Denver?

There is no shared working-hours window because of the +9h 30m gap. The closest option is 1:00 PM in Denver, which is 10:30 PM in Tehran.

Which is ahead, Denver or Tehran?

Denver is 9 hours 30 minutes ahead of Tehran. When it is 12:00 PM in Denver it is 9:30 PM in Tehran.

Do Denver and Tehran use different time zones?

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

Does daylight saving time affect the Denver–Tehran difference?

Yes at the moment: Denver is on daylight saving time and Tehran is not, so the +9h 30m gap shifts by an hour when exactly one of them changes clocks.

Which other cities share Denver's time zone?

MDT also covers Denver, Phoenix, Salt Lake City, Calgary, Edmonton, Albuquerque, El Paso, Tucson and 2 more.

Which countries use MDT, Denver's zone?

MDT is used in United States (Mountain), Canada (Alberta), Mexico (Chihuahua, Sonora).

Is there a day difference between Denver and Tehran?

Not normally. The +9h 30m gap only pushes the date over for late-evening times.

What is the time difference between Denver and Tehran?

Tehran is +9h 30m from Denver.

What timezone is Denver in?

Denver operates on Mountain Time (MST/MDT), 2 hours behind New York. As a tech and aerospace hub, Denver bridges West Coast and Central US business hours.

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 are the business hours in Denver?

Standard business hours in Denver are 8:00 AM - 5:00 PM MST.

What are the business hours in Tehran?

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

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

The best overlap for a call is when both cities are in business hours. Denver works 8:00 AM - 5:00 PM MST and Tehran works 8:00 AM - 4:00 PM IRST (+9h 30m difference). Try scheduling during the overlapping window for maximum convenience.

What currencies are used in Denver and Tehran?

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

How do Denver and Tehran compare in size?

Denver has a population of approximately 715,000 (metro: 2.9 million), while Tehran has approximately 9.4 million (metro: 16.8 million).

What are the major landmarks in Denver and Tehran?

Denver is known for Red Rocks Amphitheatre, Denver Art Museum, Union Station. Tehran is famous for Azadi Tower, Golestan Palace, Grand Bazaar.

Do Denver and Tehran have stock exchanges?

Yes. Denver has the N/A (Uses NYSE/NASDAQ) and Tehran has the TSE (Tehran Stock Exchange). The +9h 30m time difference affects trading hour overlaps between these exchanges.

Which countries use MST (Mountain Standard Time)?

MST is used in United States (Mountain), Canada (Alberta), Mexico (Chihuahua, Sonora).

Does MST observe daylight saving time?

Yes, MST switches to MDT during summer months.

What are some interesting facts about MST?

Arizona does not observe daylight saving time, staying on MST year-round. The Navajo Nation in Arizona does observe DST, unlike the rest of the state.