BST to AST
-5hBST
BSTSOURCEAST
ASTGreen rows indicate typical business hours (9 AM - 5 PM)
BST and AST on the World Map
The map below highlights the BST (British Summer Time) and AST (Atlantic Standard Time) timezone regions across the globe.
BST – British Summer Time
UTC+01:00British Summer Time (BST, UTC+01:00) is the daylight saving period in the United Kingdom, running from late March to late October.
- •BST runs from the last Sunday in March to the last Sunday in October.
- •BST is exactly one hour ahead of GMT, the UK's standard time.
- •During BST, London is 4 hours ahead of New York while the US is on Eastern Daylight Time.
- •The Isle of Man and the Channel Islands also observe BST.
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.
Everything You Need to Know About BST and AST Time
BST runs on British Summer Time (BST) at UTC+01:00. AST runs on Atlantic Standard Time (AST) at UTC-04:00. That puts BST 5 hours behind AST — a difference of -5h at the current offsets.
In practice, when it is 9:00 AM in BST it is 4:00 AM in AST. Midnight in BST is 7:00 PM in AST. Neither zone observes daylight saving time, so the offset between them stays constant all year.
BST to AST time conversion table
| BST (BST) | AST (AST) | Day |
|---|---|---|
| 12:00 AM | 7:00 PM | previous day |
| 6:00 AM | 1:00 AM | same day |
| 7:00 AM | 2:00 AM | same day |
| 8:00 AM | 3:00 AM | same day |
| 9:00 AM | 4:00 AM | same day |
| 12:00 PM | 7:00 AM | same day |
| 3:00 PM | 10:00 AM | same day |
| 5:00 PM | 12:00 PM | same day |
| 6:00 PM | 1:00 PM | same day |
| 9:00 PM | 4:00 PM | same day |
Why people convert BST to AST time
- Scheduling a call from BST to AST: a 10:00 AM start in BST lands at 5:00 AM in AST, so you can confirm the slot without doing the arithmetic yourself.
- Finding shared working hours: both BST and AST are inside the 9-to-5 working day between 2:00 PM and 5:00 PM BST time (9:00 AM–12:00 PM AST). That is roughly 3 hours of usable overlap.
- Watching a live event or market open: BST viewers need 4:00 AM in AST to catch a 9:00 AM start there, and 5:00 AM if the event is anchored to BST.
- Always state the zone abbreviation, not just the hour. "3:00 PM BST" is unambiguous; "3 PM" across a -5h gap is not.
- Block 2:00 PM–5:00 PM BST as the recurring meeting window if you work primarily from BST and need AST colleagues present.
About BST (British Summer Time)
British Summer Time (BST) is the daylight saving period in the United Kingdom, when clocks move one hour forward from Greenwich Mean Time (GMT, UTC+00:00) to UTC+01:00. It runs from the last Sunday in March to the last Sunday in October. England, Scotland, Wales and Northern Ireland all follow it, along with the Isle of Man and the Channel Islands of Jersey and Guernsey. During BST, London is one hour ahead of UTC, four hours ahead of New York on Eastern Daylight Time, and five hours ahead of New York once the United States returns to Eastern Standard Time in November. BST is also used to abbreviate Bangladesh Standard Time (UTC+06:00), which is listed separately on this site.
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 BST and AST
Both BST and AST sit inside the 9 AM – 5 PM working day between 2:00 PM–5:00 PM BST, which is 9:00 AM–12:00 PM AST. That gives roughly 3 hours of shared time — the safest window for a live call or meeting.
Business hours overlap
BST and AST overlap for about 3 hours during the working day — enough for meetings if you avoid the edges of the window.
BST is 5 hours behind AST (BST UTC+01:00 → AST UTC-04:00). The shared working window is 2:00 PM–5:00 PM BST. Remember to re-check around daylight-saving transitions.
🕐 Daylight Saving Time Info
BST
☀ Currently in DST
Standard: UTC+00:00 · DST: UTC+01:00
Clocks fall back on Sun, Oct 25, 2026
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:
Frequently Asked Questions
What is the time difference between BST and AST?
BST (BST, UTC+01:00) is 5 hours behind AST (AST, UTC-04:00). The gap is currently -5h.
How do I convert BST time to AST time?
Add -5h to BST local time. For example, 9:00 AM in BST is 4:00 AM in AST.
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 -5h offset from BST.
What is the best time to call AST from BST?
Call between 2:00 PM and 5:00 PM BST — that maps to 9:00 AM–12:00 PM AST and keeps both parties inside the working day.
Which is behind, BST or AST?
BST is 5 hours behind AST. When it is 12:00 PM in BST it is 7:00 AM in AST.
Does daylight saving time affect the BST–AST difference?
Neither zone observes daylight saving time, so the -5h offset between BST and AST is fixed all year.
Which other cities share BST's time zone?
BST also covers London, Birmingham, Manchester, Glasgow, Edinburgh, Cardiff, Belfast, Liverpool and 2 more.
Which countries use BST, BST's zone?
BST is used in United Kingdom.
Is there a day difference between BST and AST?
Not normally. The -5h gap only pushes the date over the previous day.
What is the time difference between BST and AST?
AST is -5h from BST.
What timezone is BST in?
BST operates on its local timezone.
What timezone is AST in?
AST operates on its local timezone.
Which countries use BST (British Summer Time)?
BST is used in United Kingdom.
Does BST observe daylight saving time?
Yes, BST switches to BST during summer months.
What are some interesting facts about BST?
BST runs from the last Sunday in March to the last Sunday in October. BST is exactly one hour ahead of GMT, the UK's standard time.
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 BST, what time is it in AST?
When it is 12:00 AM (midnight) in BST (BST), it is -5h later in AST (AST).
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