CST to Tehran
+9h 30mCST
CSTSOURCETehran
IRSTGreen rows indicate typical business hours (9 AM - 5 PM)
CST and IRST on the World Map
The map below highlights the CST (Central Standard Time) and IRST (Iran Standard Time) timezone regions across the globe.
CST – Central Standard Time
UTC-06:00Central Standard Time (CST) is the time zone for the central United States, Canada, and Mexico, 6 hours behind UTC.
- •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.
IRST – Iran Standard Time
UTC+03:30Iran Standard Time (IRST) is the time zone for Iran, 3 hours and 30 minutes ahead of UTC.
- •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.
About Tehran
WikipediaTehran operates on Iran Standard Time (IRST), UTC+3:30. Iran's unique half-hour offset makes Tehran time distinctive for regional business coordination.
Iran Standard Time (IRST) is one of few timezones with a 30-minute offset (UTC+3:30).
Understanding the +9h 30m Gap: CST vs Tehran
CST runs on Central Standard Time (CST) at UTC-06:00. Tehran runs on Iran Standard Time (IRST) at UTC+03:30. That puts CST 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 CST it is 6:30 PM in Tehran. Midnight in CST is 9:30 AM in Tehran. Neither zone observes daylight saving time, so the offset between them stays constant all year.
CST to Tehran time conversion table
| CST (CST) | 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 CST to Tehran time
- Scheduling a call from CST to Tehran: a 10:00 AM start in CST lands at 7:30 PM in Tehran, so you can confirm the slot without doing the arithmetic yourself.
- Handling a +9h 30m gap: CST 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 CST.
- Booking travel or deliveries: tracking Tehran local time against CST keeps pickup windows and arrival estimates honest across the +9h 30m offset.
- Always state the zone abbreviation, not just the hour. "3:00 PM CST" 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 CST takes the early slot, the next week Tehran does.
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.
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 CST 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 CST, so real-time calls need an early-morning or late-evening slot on one side.
Business hours overlap
CST and Tehran have no shared working hours because of the +9h 30m gap. Teams need to alternate early starts or rely on asynchronous handovers.
CST is 9 hours 30 minutes ahead of Tehran (CST 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
CST
☀ Currently in DST
Standard: UTC-06:00 · DST: UTC-05:00
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:
Frequently Asked Questions
What is the time difference between CST and Tehran?
CST (CST, 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 CST time to Tehran time?
Add +9h 30m to CST local time. For example, 9:00 AM in CST 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 CST.
What is the best time to call Tehran from CST?
There is no shared working-hours window because of the +9h 30m gap. The closest option is 1:00 PM in CST, which is 10:30 PM in Tehran.
Which is ahead, CST or Tehran?
CST is 9 hours 30 minutes ahead of Tehran. When it is 12:00 PM in CST it is 9:30 PM in Tehran.
Do CST and Tehran use different time zones?
CST uses CST at UTC-06:00, while Tehran (Iran) uses IRST at UTC+03:30. The IANA identifiers are America/Chicago and Asia/Tehran.
Does daylight saving time affect the CST–Tehran difference?
Neither zone observes daylight saving time, so the +9h 30m offset between CST and Tehran is fixed all year.
Which other cities share CST's time zone?
CST also covers Chicago, Houston, Dallas, San Antonio, Mexico City, Austin, Winnipeg, Memphis and 6 more.
Which countries use CST, CST's zone?
CST is used in United States (Central), Canada (Manitoba, Saskatchewan), Mexico, Guatemala, Honduras, El Salvador, Costa Rica, Nicaragua and 1 more.
Is there a day difference between CST and Tehran?
Not normally. The +9h 30m gap only pushes the date over for late-evening times.
What is the time difference between CST and Tehran?
Tehran is +9h 30m from CST.
What timezone is CST in?
CST operates on its local timezone.
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 Tehran?
Standard business hours in Tehran are 8:00 AM - 4:00 PM IRST.
Which countries use CST (Central Standard Time)?
CST is used in United States (Central), Canada (Manitoba, Saskatchewan), Mexico, Guatemala, Honduras, El Salvador, and 3 more countries.
Does CST observe daylight saving time?
Yes, CST switches to CDT during summer months.
What are some interesting facts about CST?
CST covers 20 US states fully or partially. Chicago and Houston are the two largest cities in the Central Time Zone.
Which cities are in the IRST timezone?
Major cities in the IRST timezone include Tehran, Isfahan, Mashhad, Tabriz, Shiraz, Karaj.
What is the UTC offset for IRST?
Iran Standard Time (IRST) is at UTC+03:30. During daylight saving time, it shifts to IRDT.
What should I know about the IRST timezone?
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).
When is it midnight in CST, what time is it in Tehran?
When it is 12:00 AM (midnight) in CST (CST), it is +9h 30m later in Tehran (IRST).
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