AST to GMT Converter & Meeting Planner
Quick answer: 9:00 AM AST = 1:00 PM GMT (fixed -04:00 standard offset — not DST-adjusted). Use the interactive converter below for DST-aware local-time scheduling.
Planning a call or meeting between Atlantic Standard Time (AST) and Greenwich Mean Time (GMT)? You need to account for the standard time difference. Greenwich Mean Time is normally 4 hours ahead of Atlantic Standard Time. Whether you are coordinating between teams in Halifax and San Juan and London and Dublin, our live tool has you covered. Use our interactive overlap studio below to find the perfect waking hours for both regions, taking into account any seasonal Daylight Saving Time (DST) changes.
24-Hour Conversion Table
Quick reference: 12:00 AM AST = 4:00 AM GMT. The full 24-hour AST to GMT table below uses fixed standard offsets for exact abbreviation searches.
Example: 3:00 PM AST = 7:00 PM GMT.
| AST Time | GMT Time |
|---|---|
| 12:00 AM (00:00) | 4:00 AM (04:00) |
| 1:00 AM (01:00) | 5:00 AM (05:00) |
| 2:00 AM (02:00) | 6:00 AM (06:00) |
| 3:00 AM (03:00) | 7:00 AM (07:00) |
| 4:00 AM (04:00) | 8:00 AM (08:00) |
| 5:00 AM (05:00) | 9:00 AM (09:00) |
| 6:00 AM (06:00) | 10:00 AM (10:00) |
| 7:00 AM (07:00) | 11:00 AM (11:00) |
| 8:00 AM (08:00) | 12:00 PM (12:00) |
| 9:00 AM (09:00) | 1:00 PM (13:00) |
| 10:00 AM (10:00) | 2:00 PM (14:00) |
| 11:00 AM (11:00) | 3:00 PM (15:00) |
| 12:00 PM (12:00) | 4:00 PM (16:00) |
| 1:00 PM (13:00) | 5:00 PM (17:00) |
| 2:00 PM (14:00) | 6:00 PM (18:00) |
| 3:00 PM (15:00) | 7:00 PM (19:00) |
| 4:00 PM (16:00) | 8:00 PM (20:00) |
| 5:00 PM (17:00) | 9:00 PM (21:00) |
| 6:00 PM (18:00) | 10:00 PM (22:00) |
| 7:00 PM (19:00) | 11:00 PM (23:00) |
| 8:00 PM (20:00) | 12:00 AM (00:00)+1 day |
| 9:00 PM (21:00) | 1:00 AM (01:00)+1 day |
| 10:00 PM (22:00) | 2:00 AM (02:00)+1 day |
| 11:00 PM (23:00) | 3:00 AM (03:00)+1 day |
Best time to call London from Halifax
For most work calls, compare the normal business day in Halifax (AST) with the business day in London (GMT). AST commonly covers North America, Caribbean, while GMT is mainly associated with Europe, Africa.
⚠️ Note: 2026-07-05 is not a normal workday in one or both regions based on their configured calendar. The overlap below should be treated as a reference, not a guaranteed office-hours window.
✅ The most practical overlap on 2026-07-05 is usually 9:00 AM - 1:00 PM AST, which corresponds to 1:00 PM - 5:00 PM GMT. This window sits inside the typical AST workday (9:00 AM - 5:00 PM) and the GMT workday (9:00 AM - 5:00 PM).
- DST Safety: AST or GMT may shift during Daylight Saving Time. Always confirm the converted time for your specific date.
- London Stock Exchange: 08:00-16:30 local time in London.
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Frequently Asked Questions
What is the time difference between AST and GMT?
During standard time, Greenwich Mean Time is 4 hours ahead of Atlantic Standard Time.
Does the Caribbean observe Daylight Saving Time?
The vast majority of Caribbean nations and territories — including Puerto Rico, the Dominican Republic, the US Virgin Islands, Trinidad and Tobago, and Barbados — do not observe Daylight Saving Time and remain on AST (UTC-4) year-round. This means these territories share the same clock as Halifax only during the Atlantic Standard Time window in winter, diverging by one hour once Canada and Bermuda advance to ADT each spring.
What is the difference between AST and ADT?
AST (Atlantic Standard Time) is the standard winter offset at UTC-4:00, observed from the first Sunday in November through the second Sunday in March across all AST regions. ADT (Atlantic Daylight Time) is the summer offset at UTC-3:00, applied by Eastern Canadian provinces and Bermuda when they advance their clocks by one hour during Daylight Saving Time.
What is the difference between GMT and BST?
GMT (Greenwich Mean Time) is the UK's standard winter offset at UTC+0, observed from the last Sunday in October through the last Sunday in March. BST (British Summer Time) is the daylight saving offset at UTC+1, applied each summer when clocks advance one hour.
Is GMT the same as UTC?
GMT and UTC share exactly the same numerical offset — both represent UTC+00:00 — but they are fundamentally different in nature. UTC is an atomic-clock-based international time standard used as the global reference, while GMT is a geographic time zone legally observed by specific countries including the United Kingdom and Ireland during winter months.