AST to CST Converter & Meeting Planner
Quick answer: 9:00 AM AST = 7:00 AM CST (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 Standard Time (CST)? You need to account for the standard time difference. Central Standard Time is normally 2 hours behind Atlantic Standard Time. Whether you are coordinating between teams in Halifax and San Juan and Chicago and Dallas, 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 = 10:00 PM CST. The full 24-hour AST to CST table below uses fixed standard offsets for exact abbreviation searches.
Example: 3:00 PM AST = 1:00 PM CST.
| AST Time | CST Time |
|---|---|
| 12:00 AM (00:00) | 10:00 PM (22:00)-1 day |
| 1:00 AM (01:00) | 11:00 PM (23:00)-1 day |
| 2:00 AM (02:00) | 12:00 AM (00:00) |
| 3:00 AM (03:00) | 1:00 AM (01:00) |
| 4:00 AM (04:00) | 2:00 AM (02:00) |
| 5:00 AM (05:00) | 3:00 AM (03:00) |
| 6:00 AM (06:00) | 4:00 AM (04:00) |
| 7:00 AM (07:00) | 5:00 AM (05:00) |
| 8:00 AM (08:00) | 6:00 AM (06:00) |
| 9:00 AM (09:00) | 7:00 AM (07:00) |
| 10:00 AM (10:00) | 8:00 AM (08:00) |
| 11:00 AM (11:00) | 9:00 AM (09:00) |
| 12:00 PM (12:00) | 10:00 AM (10:00) |
| 1:00 PM (13:00) | 11:00 AM (11:00) |
| 2:00 PM (14:00) | 12:00 PM (12:00) |
| 3:00 PM (15:00) | 1:00 PM (13:00) |
| 4:00 PM (16:00) | 2:00 PM (14:00) |
| 5:00 PM (17:00) | 3:00 PM (15:00) |
| 6:00 PM (18:00) | 4:00 PM (16:00) |
| 7:00 PM (19:00) | 5:00 PM (17:00) |
| 8:00 PM (20:00) | 6:00 PM (18:00) |
| 9:00 PM (21:00) | 7:00 PM (19:00) |
| 10:00 PM (22:00) | 8:00 PM (20:00) |
| 11:00 PM (23:00) | 9:00 PM (21:00) |
Best time to call Chicago from Halifax
For most work calls, compare the normal business day in Halifax (AST) with the business day in Chicago (CST). AST commonly covers North America, Caribbean, while CST is mainly associated with North America, Central America.
⚠️ 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 11:00 AM - 5:00 PM AST, which corresponds to 9:00 AM - 3:00 PM CST. This window sits inside the typical AST workday (9:00 AM - 5:00 PM) and the CST workday (9:00 AM - 5:00 PM).
- DST Safety: AST or CST may shift during Daylight Saving Time. Always confirm the converted time for your specific date.
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Frequently Asked Questions
What is the time difference between AST and CST?
During standard time, Central Standard Time is 2 hours behind 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.
Is CST the same as Central Time (CT)?
Central Time (CT) is the umbrella term for the zone, while CST and CDT refer to its two seasonal offsets. CST (UTC-6) applies during standard time from November through March, and CDT (UTC-5) applies during Daylight Saving Time from March through November.
Does Mexico City use CST?
Mexico City operates on UTC-6, the same offset as CST, but it does not observe Daylight Saving Time following Mexico's elimination of the practice under a 2022 law. This means Mexico City stays at UTC-6 year-round while US and Canadian Central Time cities shift to UTC-5 each summer.