AST
Disambiguation — Atlantic Canada/Caribbean (UTC-4) or Arabia (UTC+3).
Multiple time zones share this abbreviation
AST can refer to different time zones depending on the region. Choose the one you mean:
Standard / daylight pair
ADT · UTC−3 — March–November in Atlantic Canada and Bermuda
Where this abbreviation is used
| Meaning | Offset | Region |
|---|---|---|
| Atlantic Standard Time | UTC−4 | Caribbean islands, US Virgin Islands, Puerto Rico, and Maritime Canada. |
| Arabia Standard Time | UTC+3 | Saudi Arabia, Iraq, Kuwait, Qatar, Bahrain, and Yemen. |
| Amazon Standard Time | UTC−4 | Brazilian states including Roraima, Rondônia, and parts of Amazonas. |
Countries using this zone
- Saudi Arabia
- Iraq
- Kuwait
- Qatar
- Bahrain
- Yemen
- Dominican Republic
- Barbados
- Antigua and Barbuda
- Saint Lucia
- Dominica
- Grenada
- Saint Vincent and the Grenadines
Principal cities
- Riyadh
- Baghdad
- Kuwait City
- San Juan
- Halifax
- Doha
- Santo Domingo
History
Canada adopted Atlantic Standard Time in the early 20th century to harmonize maritime commerce with international shipping. In the Middle East, most countries transitioned from solar-based time to Arabia Standard Time (UTC+3) during the 1950s and 1960s to support modern aviation. Recently, Jordan and Syria made UTC+3 their permanent year-round offset, effectively aligning with the Arabian variant of this zone.
Frequently Asked Questions
Atlantic Standard Time (UTC−4) is used in the Western Hemisphere, specifically in the Caribbean and parts of Canada, while Arabia Standard Time (UTC+3) is used in the Middle East. These 2 zones are 7 hours apart. Because the abbreviation AST is used for both, geographical context is essential for clarity.
Atlantic Standard Time (AST) represents the standard time offset of UTC−4, whereas Atlantic Daylight Time (ADT) is the daylight saving offset of UTC−3. Locations in Atlantic Canada and Bermuda switch to ADT on the second Sunday of March. They return to AST on the first Sunday of November.
Arabia Standard Time (UTC+3) does not observe daylight saving time and remains fixed year-round across the Arabian Peninsula. This permanent offset is used by countries like Saudi Arabia, Kuwait, and Qatar. It simplifies scheduling for religious activities and regional trade by maintaining a consistent 3-hour lead over UTC.
Several Caribbean nations, including the Dominican Republic, Puerto Rico, Barbados, and Trinidad and Tobago, utilize Atlantic Standard Time (UTC−4) throughout the entire year. These regions do not observe daylight saving time due to their tropical proximity. This ensures that their local time remains consistent relative to the solar cycle.
Yes, the United States territories of Puerto Rico and the US Virgin Islands officially observe Atlantic Standard Time. Because these islands are located at lower latitudes, they do not participate in daylight saving time. They maintain a UTC−4 offset, making them 1 hour ahead of the US East Coast during winter.