AST to GMT Time Converter

When it is 9:00 AM AST, it is 1:00 PM GMT. Greenwich Mean Time (GMT, UTC+0) is 4 hours ahead of Atlantic Standard Time (AST, UTC-4). Your working-hours overlap window is 9:00 AM–1:00 PM AST (1:00 PM–5:00 PM GMT).

AST to GMT Conversion Table

Major Cities Using AST and GMT

Atlantic Standard Time (AST): Halifax, Saint John, Moncton.

Greenwich Mean Time (GMT): London, Manchester, Dublin, Edinburgh.

How many hours between AST and GMT?

AST is UTC-4 and GMT is UTC+0, a difference of 4 hours. GMT is ahead of AST. This difference can shift by an hour in either direction during Daylight Saving Time transitions — if one zone observes DST and the other doesn't, the offset narrows or widens for part of the year.

Business Hours Overlap: AST ↔ GMT

Assuming a 9:00 AM – 5:00 PM workday on each side, your working-hours overlap window is 9:00 am–1:00 pm ast (1:00 pm–5:00 pm gmt). To visualize this instantly for any pair of cities, use the visual meeting planner or the timezone overlap finder — both highlight the green overlap window on a live timeline.

Does AST observe Daylight Saving Time?

Atlantic Standard Time (AST) is based on the America/Halifax IANA timezone. DST observance depends on the jurisdiction — for example, most of the continental US switches between standard and daylight time, while India, Japan, and most of Southeast Asia do not observe DST at all. WorldClock.lol uses the authoritative IANA timezone database, so every conversion automatically accounts for the correct DST rules on the date you're converting.

When is 9 AM AST in GMT?

When it is 9:00 AM in Atlantic Standard Time (AST, UTC-4), it is 1:00 PM in Greenwich Mean Time (GMT). For other times of day, scan the conversion table above or drop into the interactive converter to pick an exact minute. The converter handles both standard and daylight variants correctly.

How to Use This AST to GMT Converter

1. Type or drag any time in the AST input above — the GMT equivalent updates instantly.
2. Check the day indicator. When the converted time crosses midnight, the tool shows +1 day or −1 day so you don't book a meeting on the wrong date.
3. Copy the shareable URL to send the specific conversion to a colleague — the link preserves your exact selection.
4. Switch directions by swapping the input zones, or open GMT to AST for the reverse.

Related AST Converters

• AST to EST
• AST to PST
• AST to UTC
• AST to IST
• AST to JST
• AST to CET

Related GMT Converters

• EST to GMT
• PST to GMT
• UTC to GMT
• IST to GMT
• JST to GMT
• CET to GMT

More Time Tools

• All Time Zone Converters — browse every supported pair
• About AST (Atlantic Standard Time) — current time, cities, DST rules
• About GMT (Greenwich Mean Time) — current time, cities, DST rules
• Meeting Planner — find the best time for a multi-city meeting
• Best Time to Call — optimal calling windows between any two cities
• UTC Time Now — the reference point for every conversion
• DST Schedule 2026 — every daylight-saving transition this year