Colombo to Tehran
-2hColombo
ISTSOURCETehran
IRSTGreen rows indicate typical business hours (9 AM - 5 PM)
IST and IRST on the World Map
The map below highlights the IST (India Standard Time) and IRST (Iran Standard Time) timezone regions across the globe.
IST – India Standard Time
UTC+05:30India Standard Time (IST) is the time zone for India and Sri Lanka, 5 hours and 30 minutes ahead of UTC.
- •India is 10 hours 30 minutes ahead of EST and 5 hours 30 minutes ahead of GMT.
- •India uses a single time zone despite spanning 30° of longitude.
- •IST is one of only a handful of time zones with a 30-minute offset.
- •IST is the most populous single time zone in the world with over 1.4 billion people.
- •The Bombay Stock Exchange (BSE) and National Stock Exchange (NSE) operate on IST.
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 Colombo
WikipediaColombo operates on Sri Lanka Time (SLST), UTC+5:30. Sharing India's timezone, Colombo is a key South Asian trade and tourism hub.
Sri Lanka Standard Time (SLST) uses UTC+5:30, same offset as India.
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).
Comparing Time Zones: Colombo and Tehran
Colombo runs on India Standard Time (IST) at UTC+05:30. Tehran runs on Iran Standard Time (IRST) at UTC+03:30. That puts Colombo 2 hours behind Tehran — a difference of -2h at the current offsets.
In practice, when it is 9:00 AM in Colombo it is 7:00 AM in Tehran. Midnight in Colombo is 10:00 PM in Tehran. Neither zone observes daylight saving time, so the offset between them stays constant all year.
Colombo to Tehran time conversion table
| Colombo (IST) | Tehran (IRST) | Day |
|---|---|---|
| 12:00 AM | 10:00 PM | previous day |
| 6:00 AM | 4:00 AM | same day |
| 7:00 AM | 5:00 AM | same day |
| 8:00 AM | 6:00 AM | same day |
| 9:00 AM | 7:00 AM | same day |
| 12:00 PM | 10:00 AM | same day |
| 3:00 PM | 1:00 PM | same day |
| 5:00 PM | 3:00 PM | same day |
| 6:00 PM | 4:00 PM | same day |
| 9:00 PM | 7:00 PM | same day |
Why people convert Colombo to Tehran time
- Scheduling a call from Colombo to Tehran: a 10:00 AM start in Colombo lands at 8:00 AM in Tehran, so you can confirm the slot without doing the arithmetic yourself.
- Finding shared working hours: both Colombo and Tehran are inside the 9-to-5 working day between 11:00 AM and 5:00 PM IST time (9:00 AM–3:00 PM IRST). That is roughly 6 hours of usable overlap.
- Coordinating a Colombo-based team with Tehran 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 IST" is unambiguous; "3 PM" across a -2h gap is not.
- Block 11:00 AM–5:00 PM IST as the recurring meeting window if you work primarily from Colombo and need Tehran colleagues present.
About IST (India Standard Time)
India Standard Time (IST) is the time observed throughout India and Sri Lanka. It is based on the 82.5°E meridian, passing through Mirzapur in Uttar Pradesh. India uses a single time zone despite spanning roughly 30° of longitude, which has been debated. IST does not observe daylight saving time. India is the world's most populous country, making IST one of the most-used time zones globally. The IT outsourcing industry and call centers operate primarily on IST, making the EST-to-IST conversion one of the most searched timezone conversions.
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 Colombo and Tehran
Both Colombo and Tehran sit inside the 9 AM – 5 PM working day between 11:00 AM–5:00 PM IST, which is 9:00 AM–3:00 PM IRST. That gives roughly 6 hours of shared time — the safest window for a live call or meeting.
Business hours overlap
Colombo and Tehran share 6 hours of working-hours overlap (11:00 AM–5:00 PM IST), so scheduling a live meeting is straightforward.
Colombo is 2 hours behind Tehran (IST UTC+05:30 → IRST UTC+03:30). The shared working window is 11:00 AM–5:00 PM IST. Remember to re-check around daylight-saving transitions.
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 Colombo and Tehran?
Colombo (IST, UTC+05:30) is 2 hours behind Tehran (IRST, UTC+03:30). The gap is currently -2h.
How do I convert Colombo time to Tehran time?
Add -2h to Colombo local time. For example, 9:00 AM in Colombo is 7:00 AM 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 -2h offset from Colombo.
What is the best time to call Tehran from Colombo?
Call between 11:00 AM and 5:00 PM IST — that maps to 9:00 AM–3:00 PM IRST and keeps both parties inside the working day.
Which is behind, Colombo or Tehran?
Colombo is 2 hours behind Tehran. When it is 12:00 PM in Colombo it is 10:00 AM in Tehran.
Do Colombo and Tehran use different time zones?
Colombo (Sri Lanka) uses IST at UTC+05:30, while Tehran (Iran) uses IRST at UTC+03:30. The IANA identifiers are Asia/Colombo and Asia/Tehran.
Does daylight saving time affect the Colombo–Tehran difference?
Neither zone observes daylight saving time, so the -2h offset between Colombo and Tehran is fixed all year.
Which other cities share Colombo's time zone?
IST also covers Mumbai, Delhi, Bangalore, Kolkata, Chennai, Hyderabad, Pune, Ahmedabad and 4 more.
Which countries use IST, Colombo's zone?
IST is used in India, Sri Lanka.
Is there a day difference between Colombo and Tehran?
Not normally. The -2h gap only pushes the date over the previous day.
What is the time difference between Colombo and Tehran?
Tehran is -2h from Colombo.
What timezone is Colombo in?
Colombo operates on Sri Lanka Time (SLST), UTC+5:30. Sharing India's timezone, Colombo is a key South Asian trade and tourism hub.
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 Colombo?
Standard business hours in Colombo are 9:00 AM - 5:00 PM IST.
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 Colombo and Tehran?
The best overlap for a call is when both cities are in business hours. Colombo works 9:00 AM - 5:00 PM IST and Tehran works 8:00 AM - 4:00 PM IRST (-2h difference). Try scheduling during the overlapping window for maximum convenience.
What currencies are used in Colombo and Tehran?
Colombo uses LKR (Rs) while Tehran uses IRR (﷼). Check current exchange rates when planning travel or business between these cities.
How do Colombo and Tehran compare in size?
Colombo has a population of approximately 752,000 (metro: 5.6 million), while Tehran has approximately 9.4 million (metro: 16.8 million).
What are the major landmarks in Colombo and Tehran?
Colombo is known for Galle Face Green, Gangaramaya Temple, Colombo Lotus Tower. Tehran is famous for Azadi Tower, Golestan Palace, Grand Bazaar.
Do Colombo and Tehran have stock exchanges?
Yes. Colombo has the CSE (Colombo Stock Exchange) and Tehran has the TSE (Tehran Stock Exchange). The -2h time difference affects trading hour overlaps between these exchanges.
Which countries use IST (India Standard Time)?
IST is used in India, Sri Lanka.
Does IST observe daylight saving time?
No, IST does not observe daylight saving time and remains at UTC+05:30 year-round.
What are some interesting facts about IST?
India is 10 hours 30 minutes ahead of EST and 5 hours 30 minutes ahead of GMT. India uses a single time zone despite spanning 30° of longitude.
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 Colombo, what time is it in Tehran?
When it is 12:00 AM (midnight) in Colombo (IST), it is -2h later in Tehran (IRST).
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