AST to Colombo
+9h 30mAST
ASTSOURCEColombo
ISTGreen rows indicate typical business hours (9 AM - 5 PM)
AST and IST on the World Map
The map below highlights the AST (Atlantic Standard Time) and IST (India Standard Time) timezone regions across the globe.
AST – Atlantic Standard Time
UTC-04:00Atlantic Standard Time (AST) is the time zone for the Canadian Atlantic provinces and the Caribbean, 4 hours behind UTC.
- •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.
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.
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.
AST to Colombo Time Difference – Complete Guide
AST runs on Atlantic Standard Time (AST) at UTC-04:00. Colombo runs on India Standard Time (IST) at UTC+05:30. That puts AST 9 hours 30 minutes ahead of Colombo — a difference of +9h 30m at the current offsets.
In practice, when it is 9:00 AM in AST it is 6:30 PM in Colombo. Midnight in AST is 9:30 AM in Colombo. Neither zone observes daylight saving time, so the offset between them stays constant all year.
AST to Colombo time conversion table
| AST (AST) | Colombo (IST) | 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 AST to Colombo time
- Scheduling a call from AST to Colombo: a 10:00 AM start in AST lands at 7:30 PM in Colombo, so you can confirm the slot without doing the arithmetic yourself.
- Handling a +9h 30m gap: AST and Colombo 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 Colombo is 6:30 PM in AST.
- Coordinating a AST-based team with Colombo 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 AST" 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 AST takes the early slot, the next week Colombo does.
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.
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.
Best time to call between AST and Colombo
With a +9h 30m offset there is no overlap inside a normal 9 AM – 5 PM day. Colombo opens at 9:00 AM IST, which is 6:30 PM in AST, so real-time calls need an early-morning or late-evening slot on one side.
Business hours overlap
AST and Colombo have no shared working hours because of the +9h 30m gap. Teams need to alternate early starts or rely on asynchronous handovers.
AST is 9 hours 30 minutes ahead of Colombo (AST UTC-04:00 → IST UTC+05:30). 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
AST
☀ Currently in DST
Standard: UTC-04:00 · DST: UTC-03:00
Clocks fall back on Sun, Nov 1, 2026
Colombo
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 AST and Colombo?
AST (AST, UTC-04:00) is 9 hours 30 minutes ahead of Colombo (IST, UTC+05:30). The gap is currently +9h 30m.
How do I convert AST time to Colombo time?
Add +9h 30m to AST local time. For example, 9:00 AM in AST is 6:30 PM in Colombo.
What time is it in Colombo right now?
Colombo uses IST at UTC+05:30. Use the live converter at the top of this page — it updates in real time and already accounts for the +9h 30m offset from AST.
What is the best time to call Colombo from AST?
There is no shared working-hours window because of the +9h 30m gap. The closest option is 1:00 PM in AST, which is 10:30 PM in Colombo.
Which is ahead, AST or Colombo?
AST is 9 hours 30 minutes ahead of Colombo. When it is 12:00 PM in AST it is 9:30 PM in Colombo.
Do AST and Colombo use different time zones?
AST uses AST at UTC-04:00, while Colombo (Sri Lanka) uses IST at UTC+05:30. The IANA identifiers are America/Halifax and Asia/Colombo.
Does daylight saving time affect the AST–Colombo difference?
Neither zone observes daylight saving time, so the +9h 30m offset between AST and Colombo is fixed all year.
Which other cities share AST's time zone?
AST also covers Halifax, San Juan, Santo Domingo, Caracas, La Paz, Fredericton, Charlottetown.
Which countries use AST, AST's zone?
AST is used in Canada (Atlantic provinces), Puerto Rico, US Virgin Islands, Dominican Republic, Venezuela, Bolivia, Barbados, Trinidad and Tobago.
Is there a day difference between AST and Colombo?
Not normally. The +9h 30m gap only pushes the date over for late-evening times.
What is the time difference between AST and Colombo?
Colombo is +9h 30m from AST.
What timezone is AST in?
AST operates on its local timezone.
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 are the business hours in Colombo?
Standard business hours in Colombo are 9:00 AM - 5:00 PM IST.
Which countries use AST (Atlantic Standard Time)?
AST is used in Canada (Atlantic provinces), Puerto Rico, US Virgin Islands, Dominican Republic, Venezuela, Bolivia, and 2 more countries.
Does AST observe daylight saving time?
Yes, AST switches to ADT during summer months.
What are some interesting facts about AST?
Puerto Rico uses AST year-round and does not observe DST. AST is 1 hour ahead of EST.
Which cities are in the IST timezone?
Major cities in the IST timezone include Mumbai, Delhi, Bangalore, Kolkata, Chennai, Hyderabad, Pune, Ahmedabad.
What is the UTC offset for IST?
India Standard Time (IST) is at UTC+05:30.
What should I know about the IST timezone?
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.
When is it midnight in AST, what time is it in Colombo?
When it is 12:00 AM (midnight) in AST (AST), it is +9h 30m later in Colombo (IST).
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