Инструменты Intosoft

Colombo to AST

-9h 30m

Colombo

ISTSOURCE
Sri Lanka · UTC+05:30
HH12
:
MM00
  
12:00 (24-hr)
12 AM6 AM12 PM6 PM12 AM

AST

AST
UTC-03:00☀ DST active
HH02
:
MM30
  
02:30 (24-hr)
12 AM6 AM12 PM6 PM12 AM
Colombo
AST
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)

IST and AST on the World Map

The map below highlights the IST (India Standard Time) and AST (Atlantic Standard Time) timezone regions across the globe.

ISTASTMumbaiDelhiBangaloreKolkataHalifaxSan JuanSanto DomingoCaracas
IST Zone
→
AST Zone

Explore all world timezones interactively →

IST – India Standard Time

UTC+05:30

India Standard Time (IST) is the time zone for India and Sri Lanka, 5 hours and 30 minutes ahead of UTC.

Countries in IST
IndiaSri Lanka
Major Cities in IST
MumbaiDelhiBangaloreKolkataChennaiHyderabadPuneAhmedabadColomboJaipurLucknowSurat
Key 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.
  • •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.
Daylight Saving:No – UTC+05:30 year-round
Learn more about IST on Wikipedia

AST – Atlantic Standard Time

UTC-04:00

Atlantic Standard Time (AST) is the time zone for the Canadian Atlantic provinces and the Caribbean, 4 hours behind UTC.

Countries in AST
Canada (Atlantic provinces)Puerto RicoUS Virgin IslandsDominican RepublicVenezuelaBoliviaBarbadosTrinidad and Tobago
Major Cities in AST
HalifaxSan JuanSanto DomingoCaracasLa PazFrederictonCharlottetown
Key Facts about AST
  • •Puerto Rico uses AST year-round and does not observe DST.
  • •AST is 1 hour ahead of EST.
  • •Halifax, the capital of Nova Scotia, is the largest city in AST Canada.
Daylight Saving:Yes – switches to ADT
Learn more about AST on Wikipedia

About Colombo

Wikipedia

Colombo operates on Sri Lanka Time (SLST), UTC+5:30. Sharing India's timezone, Colombo is a key South Asian trade and tourism hub.

Population:752,000
Metro:5.6 million
Business Hours:9:00 AM - 5:00 PM IST
Currency:LKR (Rs)
Stock Exchange:CSE (Colombo Stock Exchange)
Key Landmarks
Galle Face GreenGangaramaya TempleColombo Lotus TowerIndependence SquareDutch Hospital
Did You Know?

Sri Lanka Standard Time (SLST) uses UTC+5:30, same offset as India.

Learn more about IST timezone →

Everything You Need to Know About Colombo and AST Time

Colombo runs on India Standard Time (IST) at UTC+05:30. AST runs on Atlantic Standard Time (AST) at UTC-04:00. That puts Colombo 9 hours 30 minutes behind AST — a difference of -9h 30m at the current offsets.

In practice, when it is 9:00 AM in Colombo it is 11:30 PM in AST on the previous day. Midnight in Colombo is 2:30 PM in AST. Neither zone observes daylight saving time, so the offset between them stays constant all year.

Colombo to AST time conversion table

Colombo (IST)AST (AST)Day
12:00 AM2:30 PMprevious day
6:00 AM8:30 PMprevious day
7:00 AM9:30 PMprevious day
8:00 AM10:30 PMprevious day
9:00 AM11:30 PMprevious day
12:00 PM2:30 AMsame day
3:00 PM5:30 AMsame day
5:00 PM7:30 AMsame day
6:00 PM8:30 AMsame day
9:00 PM11:30 AMsame day

Why people convert Colombo to AST time

  • Scheduling a call from Colombo to AST: a 10:00 AM start in Colombo lands at 12:30 AM in AST, so you can confirm the slot without doing the arithmetic yourself.
  • Handling a -9h 30m gap: Colombo and AST 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 AST is 11:30 PM in Colombo.
  • Keeping family and friends in sync: knowing that 8:00 PM in Colombo is 10:30 AM in AST makes it easy to avoid calling at 3 AM.
  • Always state the zone abbreviation, not just the hour. "3:00 PM IST" 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 Colombo takes the early slot, the next week AST does.

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 AST (Atlantic Standard Time)

Atlantic Standard Time (AST) covers Canada's Atlantic provinces (Nova Scotia, New Brunswick, Prince Edward Island, and most of Labrador), as well as several Caribbean nations. Puerto Rico and the US Virgin Islands use AST year-round without daylight saving time. The Canadian provinces switch to Atlantic Daylight Time (ADT) in summer.

Best time to call between Colombo and AST

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

Business hours overlap

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

Colombo is 9 hours 30 minutes behind AST (IST UTC+05:30 → AST UTC-04:00). 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

Colombo

Does not observe DST

AST

☀ Currently in DST

Standard: UTC-04:00 · DST: UTC-03:00

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 Colombo and AST?

Colombo (IST, UTC+05:30) is 9 hours 30 minutes behind AST (AST, UTC-04:00). The gap is currently -9h 30m.

How do I convert Colombo time to AST time?

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

What time is it in AST right now?

AST uses AST at UTC-04:00. Use the live converter at the top of this page — it updates in real time and already accounts for the -9h 30m offset from Colombo.

What is the best time to call AST from Colombo?

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

Which is behind, Colombo or AST?

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

Do Colombo and AST use different time zones?

Colombo (Sri Lanka) uses IST at UTC+05:30, while AST uses AST at UTC-04:00. The IANA identifiers are Asia/Colombo and America/Halifax.

Does daylight saving time affect the Colombo–AST difference?

Neither zone observes daylight saving time, so the -9h 30m offset between Colombo and AST 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 AST?

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

What is the time difference between Colombo and AST?

AST is -9h 30m 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 AST in?

AST operates on its local timezone.

What are the business hours in Colombo?

Standard business hours in Colombo are 9:00 AM - 5:00 PM IST.

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 AST timezone?

Major cities in the AST timezone include Halifax, San Juan, Santo Domingo, Caracas, La Paz, Fredericton, Charlottetown.

What is the UTC offset for AST?

Atlantic Standard Time (AST) is at UTC-04:00. During daylight saving time, it shifts to ADT.

What should I know about the AST timezone?

Puerto Rico uses AST year-round and does not observe DST. AST is 1 hour ahead of EST.

When is it midnight in Colombo, what time is it in AST?

When it is 12:00 AM (midnight) in Colombo (IST), it is -9h 30m later in AST (AST).

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