UTC to AST
-4hUTC
UTCSOURCEAST
ASTGreen rows indicate typical business hours (9 AM - 5 PM)
UTC and AST on the World Map
The map below highlights the UTC (Coordinated Universal Time) and AST (Atlantic Standard Time) timezone regions across the globe.
UTC – Coordinated Universal Time
UTC+00:00Coordinated Universal Time (UTC) is the world's primary time standard, used as the basis for civil time worldwide.
- •UTC is the basis for all civil time zones worldwide.
- •The abbreviation 'UTC' is a compromise between English (CUT) and French (TUC).
- •UTC is based on atomic clocks and is accurate to within a nanosecond per day.
- •Servers and databases worldwide store timestamps in UTC to avoid timezone confusion.
- •Leap seconds are occasionally added to UTC to keep it aligned with Earth's rotation.
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.
UTC vs AST: Offsets, DST and Best Call Times
UTC runs on Coordinated Universal Time (UTC) at UTC+00:00. AST runs on Atlantic Standard Time (AST) at UTC-04:00. That puts UTC 4 hours behind AST — a difference of -4h at the current offsets.
In practice, when it is 9:00 AM in UTC it is 5:00 AM in AST. Midnight in UTC is 8:00 PM in AST. Neither zone observes daylight saving time, so the offset between them stays constant all year.
UTC to AST time conversion table
| UTC (UTC) | AST (AST) | Day |
|---|---|---|
| 12:00 AM | 8:00 PM | previous day |
| 6:00 AM | 2:00 AM | same day |
| 7:00 AM | 3:00 AM | same day |
| 8:00 AM | 4:00 AM | same day |
| 9:00 AM | 5:00 AM | same day |
| 12:00 PM | 8:00 AM | same day |
| 3:00 PM | 11:00 AM | same day |
| 5:00 PM | 1:00 PM | same day |
| 6:00 PM | 2:00 PM | same day |
| 9:00 PM | 5:00 PM | same day |
Why people convert UTC to AST time
- Scheduling a call from UTC to AST: a 10:00 AM start in UTC lands at 6:00 AM in AST, so you can confirm the slot without doing the arithmetic yourself.
- Finding shared working hours: both UTC and AST are inside the 9-to-5 working day between 1:00 PM and 5:00 PM UTC time (9:00 AM–1:00 PM AST). That is roughly 4 hours of usable overlap.
- Coordinating a UTC-based team with AST 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 UTC" is unambiguous; "3 PM" across a -4h gap is not.
- Block 1:00 PM–5:00 PM UTC as the recurring meeting window if you work primarily from UTC and need AST colleagues present.
About UTC (Coordinated Universal Time)
Coordinated Universal Time (UTC) is the primary time standard by which the world regulates clocks and time. It is effectively the successor to GMT and is based on International Atomic Time with leap seconds added to keep it synchronized with Earth's rotation. UTC is used in aviation, computing, navigation, weather forecasting, and the International Space Station. Most programming languages and databases store timestamps in UTC.
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 UTC and AST
Both UTC and AST sit inside the 9 AM – 5 PM working day between 1:00 PM–5:00 PM UTC, which is 9:00 AM–1:00 PM AST. That gives roughly 4 hours of shared time — the safest window for a live call or meeting.
Business hours overlap
UTC and AST overlap for about 4 hours during the working day — enough for meetings if you avoid the edges of the window.
UTC is 4 hours behind AST (UTC UTC+00:00 → AST UTC-04:00). The shared working window is 1:00 PM–5:00 PM UTC. Remember to re-check around daylight-saving transitions.
🕐 Daylight Saving Time Info
UTC
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:
Frequently Asked Questions
What is the time difference between UTC and AST?
UTC (UTC, UTC+00:00) is 4 hours behind AST (AST, UTC-04:00). The gap is currently -4h.
How do I convert UTC time to AST time?
Add -4h to UTC local time. For example, 9:00 AM in UTC is 5:00 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 -4h offset from UTC.
What is the best time to call AST from UTC?
Call between 1:00 PM and 5:00 PM UTC — that maps to 9:00 AM–1:00 PM AST and keeps both parties inside the working day.
Which is behind, UTC or AST?
UTC is 4 hours behind AST. When it is 12:00 PM in UTC it is 8:00 AM in AST.
Does daylight saving time affect the UTC–AST difference?
Neither zone observes daylight saving time, so the -4h offset between UTC and AST is fixed all year.
Which other cities share UTC's time zone?
UTC also covers London, Dublin, Reykjavik, Accra, Lisbon, Dakar.
Which countries use UTC, UTC's zone?
UTC is used in Used worldwide as reference, Same zone as: UK, Ireland, Iceland, Portugal, Ghana.
Is there a day difference between UTC and AST?
Not normally. The -4h gap only pushes the date over the previous day.
What is the time difference between UTC and AST?
AST is -4h from UTC.
What timezone is UTC in?
UTC operates on its local timezone.
What timezone is AST in?
AST operates on its local timezone.
Which countries use UTC (Coordinated Universal Time)?
UTC is used in Used worldwide as reference, Same zone as: UK, Ireland, Iceland, Portugal, Ghana.
Does UTC observe daylight saving time?
No, UTC does not observe daylight saving time and remains at UTC+00:00 year-round.
What are some interesting facts about UTC?
UTC is the basis for all civil time zones worldwide. The abbreviation 'UTC' is a compromise between English (CUT) and French (TUC).
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 UTC, what time is it in AST?
When it is 12:00 AM (midnight) in UTC (UTC), it is -4h later in AST (AST).
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