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 Denver

-9h 30m

IRST

IRSTSOURCE

UTC+03:30

HH12

MM00

12:00 (24-hr)

12 AM6 AM12 PM6 PM12 AM

Denver

MDT

USA · UTC-06:00☀ DST active

HH02

MM30

02:30 (24-hr)

12 AM6 AM12 PM6 PM12 AM

Quick Reference

Time Conversion Table

IRST

Denver

12:00 AM

2:30 PM-1

2:00 AM

4:30 PM-1

4:00 AM

6:30 PM-1

6:00 AM

8:30 PM-1

8:00 AM

10:30 PM-1

10:00 AM

12:30 AM

12:00 PM

2:30 AM

2:00 PM

4:30 AM

4:00 PM

6:30 AM

6:00 PM

8:30 AM

8:00 PM

10:30 AM

10:00 PM

12:30 PM

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

IRST and MDT on the World Map

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

IRST Zone

→

MDT 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

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

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 →

Time Conversion Guide: IRST to Denver

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

In practice, when it is 9:00 AM in IRST it is 11:30 PM in Denver on the previous day. Midnight in IRST is 2:30 PM in Denver.Denver observes daylight saving time while IRST does not, so the gap narrows or widens by an hour part of the year.

IRST to Denver time conversion table

IRST (IRST)	Denver (MDT)	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 IRST to Denver time

Scheduling a call from IRST to Denver: a 10:00 AM start in IRST lands at 12:30 AM in Denver, so you can confirm the slot without doing the arithmetic yourself.
Handling a -9h 30m gap: IRST and Denver 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 Denver is 11:30 PM in IRST.
Coordinating a IRST-based team with Denver 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 -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 IRST takes the early slot, the next week Denver does.
Denver: 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 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).

Best time to call between IRST and Denver

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

Business hours overlap

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

IRST is 9 hours 30 minutes behind Denver (IRST UTC+03:30 → MDT 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

IRST

Does not observe DST

Denver

☀ Currently in DST

Standard: UTC-07:00 · DST: UTC-06:00

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 IRST and Denver?

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

How do I convert IRST time to Denver time?

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

What time is it in Denver right now?

Denver uses MDT 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 IRST.

What is the best time to call Denver from IRST?

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

Which is behind, IRST or Denver?

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

Do IRST and Denver use different time zones?

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

Does daylight saving time affect the IRST–Denver difference?

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

Which other cities share IRST's time zone?

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

Which countries use IRST, IRST's zone?

IRST is used in Iran.

Is there a day difference between IRST and Denver?

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

What is the time difference between IRST and Denver?

Denver is -9h 30m from IRST.

What timezone is IRST in?

IRST operates on its local timezone.

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 are the business hours in Denver?

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

Which countries use IRST (Iran Standard Time)?

IRST is used in Iran.

Does IRST observe daylight saving time?

Yes, IRST switches to IRDT during summer months.

What are some interesting 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).

Which cities are in the MST timezone?

Major cities in the MST timezone include Denver, Phoenix, Salt Lake City, Calgary, Edmonton, Albuquerque, El Paso, Tucson.

What is the UTC offset for MST?

Mountain Standard Time (MST) is at UTC-07:00. During daylight saving time, it shifts to MDT.

What should I know about the MST timezone?

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.