AST to CAT Converter & Meeting Planner
Quick answer: 9:00 AM AST = 3:00 PM CAT (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 Central Africa Time (CAT)? You need to account for the standard time difference. Central Africa Time is normally 6 hours ahead of Atlantic Standard Time. Whether you are coordinating between teams in Halifax and San Juan and Johannesburg and Harare, 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 = 6:00 AM CAT. The full 24-hour AST to CAT table below uses fixed standard offsets for exact abbreviation searches.
Example: 3:00 PM AST = 9:00 PM CAT.
| AST Time | CAT Time |
|---|---|
| 12:00 AM (00:00) | 6:00 AM (06:00) |
| 1:00 AM (01:00) | 7:00 AM (07:00) |
| 2:00 AM (02:00) | 8:00 AM (08:00) |
| 3:00 AM (03:00) | 9:00 AM (09:00) |
| 4:00 AM (04:00) | 10:00 AM (10:00) |
| 5:00 AM (05:00) | 11:00 AM (11:00) |
| 6:00 AM (06:00) | 12:00 PM (12:00) |
| 7:00 AM (07:00) | 1:00 PM (13:00) |
| 8:00 AM (08:00) | 2:00 PM (14:00) |
| 9:00 AM (09:00) | 3:00 PM (15:00) |
| 10:00 AM (10:00) | 4:00 PM (16:00) |
| 11:00 AM (11:00) | 5:00 PM (17:00) |
| 12:00 PM (12:00) | 6:00 PM (18:00) |
| 1:00 PM (13:00) | 7:00 PM (19:00) |
| 2:00 PM (14:00) | 8:00 PM (20:00) |
| 3:00 PM (15:00) | 9:00 PM (21:00) |
| 4:00 PM (16:00) | 10:00 PM (22:00) |
| 5:00 PM (17:00) | 11:00 PM (23:00) |
| 6:00 PM (18:00) | 12:00 AM (00:00)+1 day |
| 7:00 PM (19:00) | 1:00 AM (01:00)+1 day |
| 8:00 PM (20:00) | 2:00 AM (02:00)+1 day |
| 9:00 PM (21:00) | 3:00 AM (03:00)+1 day |
| 10:00 PM (22:00) | 4:00 AM (04:00)+1 day |
| 11:00 PM (23:00) | 5:00 AM (05:00)+1 day |
Best time to call Johannesburg from Halifax
For most work calls, compare the normal business day in Halifax (AST) with the business day in Johannesburg (CAT). AST commonly covers North America, Caribbean, while CAT is mainly associated with Southern Africa, Central 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 - 12:00 PM AST, which corresponds to 2:00 PM - 5:00 PM CAT. This window sits inside the typical AST workday (9:00 AM - 5:00 PM) and the CAT workday (8:00 AM - 5:00 PM).
- DST Safety: AST or CAT may shift during Daylight Saving Time. Always confirm the converted time for your specific date.
- Johannesburg Stock Exchange (JSE): 09:00-17:00 local time in Johannesburg.
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Frequently Asked Questions
What is the time difference between AST and CAT?
During standard time, Central Africa Time is 6 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.
Does the Central Africa Time zone observe Daylight Saving Time?
None of the countries observing Central Africa Time use Daylight Saving Time. South Africa abolished DST in 1994, and no other CAT-observing nation currently applies seasonal clock changes — CAT remains permanently fixed at UTC+02:00 throughout the year.
Which major countries use Central Africa Time (CAT)?
Central Africa Time is observed by South Africa, Zimbabwe, Zambia, Botswana, Mozambique, Malawi, and Eswatini. South Africa is the zone's dominant economy, with Johannesburg functioning as the region's primary financial center and home to the Johannesburg Stock Exchange (JSE), Africa's largest equity market by capitalization.