United Kingdom to AST
-5hUnited Kingdom
BSTSOURCEAST
ASTGreen rows indicate typical business hours (9 AM - 5 PM)
BST and AST on the World Map
The map below highlights the BST (Greenwich Mean Time) and AST (Atlantic Standard Time) timezone regions across the globe.
GMT – Greenwich Mean Time
UTC+00:00Greenwich Mean Time (GMT) is the mean solar time at the Royal Observatory in Greenwich, London. It is the same as UTC+00:00.
- •GMT is based on the Prime Meridian (0° longitude) passing through Greenwich, London.
- •The Royal Observatory in Greenwich has been the reference point for GMT since 1884.
- •GMT and UTC are often used interchangeably, but UTC is based on atomic clocks.
- •Iceland uses GMT year-round and never observes daylight saving time.
- •The UK switches from GMT to BST (British Summer Time) in late March each year.
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.
United Kingdom vs AST: Offsets, DST and Best Call Times
United Kingdom runs on British Summer Time (BST) at UTC+01:00, currently observing daylight saving time. AST runs on Atlantic Standard Time (AST) at UTC-04:00. That puts United Kingdom 5 hours behind AST — a difference of -5h at the current offsets.
In practice, when it is 9:00 AM in United Kingdom it is 4:00 AM in AST. Midnight in United Kingdom is 7:00 PM in AST.United Kingdom observes daylight saving time while AST does not, so the gap narrows or widens by an hour part of the year.
United Kingdom to AST time conversion table
| United Kingdom (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 United Kingdom to AST time
- Scheduling a call from United Kingdom to AST: a 10:00 AM start in United Kingdom lands at 5:00 AM in AST, so you can confirm the slot without doing the arithmetic yourself.
- Finding shared working hours: both United Kingdom 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.
- Keeping family and friends in sync: knowing that 8:00 PM in United Kingdom is 3:00 PM in AST makes it easy to avoid calling at 3 AM.
- 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 United Kingdom and need AST colleagues present.
- United Kingdom: Clocks fall back on Sun, Oct 25, 2026. Re-check this page after that date because the offset changes and so does the -5h gap.
About GMT (Greenwich Mean Time)
Greenwich Mean Time (GMT) is the clock time at the Royal Observatory in Greenwich, London, which sits on the Prime Meridian (0° longitude). GMT serves as the reference point from which all other time zones are calculated. The United Kingdom uses GMT during winter months and switches to British Summer Time (BST, UTC+01:00) from late March to late October. Several West African nations use GMT year-round. GMT is often used interchangeably with UTC (Coordinated Universal Time), although technically they are different – UTC is based on atomic clocks while GMT is based on Earth's rotation.
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 United Kingdom and AST
Both United Kingdom 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
United Kingdom and AST overlap for about 3 hours during the working day — enough for meetings if you avoid the edges of the window.
United Kingdom 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
United Kingdom
☀ 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 United Kingdom and AST?
United Kingdom (BST, UTC+01:00) is 5 hours behind AST (AST, UTC-04:00). The gap is currently -5h.
How do I convert United Kingdom time to AST time?
Add -5h to United Kingdom local time. For example, 9:00 AM in United Kingdom 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 United Kingdom.
What is the best time to call AST from United Kingdom?
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, United Kingdom or AST?
United Kingdom is 5 hours behind AST. When it is 12:00 PM in United Kingdom it is 7:00 AM in AST.
Do United Kingdom and AST use different time zones?
United Kingdom (United Kingdom) uses BST at UTC+01:00, while AST uses AST at UTC-04:00. The IANA identifiers are Europe/London and America/Halifax.
Does daylight saving time affect the United Kingdom–AST difference?
Yes at the moment: United Kingdom is on daylight saving time and AST is not, so the -5h gap shifts by an hour when exactly one of them changes clocks.
Which other cities share United Kingdom's time zone?
BST also covers London, Dublin, Lisbon, Accra, Reykjavik, Edinburgh, Casablanca, Dakar and 5 more.
Which countries use BST, United Kingdom's zone?
BST is used in United Kingdom, Ireland, Iceland, Portugal (mainland), Ghana, Senegal, Mali, Mauritania and 7 more.
Is there a day difference between United Kingdom and AST?
Not normally. The -5h gap only pushes the date over the previous day.
What is the time difference between United Kingdom and AST?
AST is -5h from United Kingdom.
What timezone is United Kingdom in?
United Kingdom operates on its local timezone.
What timezone is AST in?
AST operates on its local timezone.
Which countries use GMT (Greenwich Mean Time)?
GMT is used in United Kingdom, Ireland, Iceland, Portugal (mainland), Ghana, Senegal, and 9 more countries.
Does GMT observe daylight saving time?
Yes, GMT switches to BST during summer months.
What are some interesting facts about GMT?
GMT is based on the Prime Meridian (0° longitude) passing through Greenwich, London. The Royal Observatory in Greenwich has been the reference point for GMT since 1884.
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 United Kingdom, what time is it in AST?
When it is 12:00 AM (midnight) in United Kingdom (GMT), it is -5h later in AST (AST).
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