AST to CST
-2hAST
ASTSOURCECST
CSTGreen rows indicate typical business hours (9 AM - 5 PM)
AST and CST on the World Map
The map below highlights the AST (Atlantic Standard Time) and CST (Central Standard Time) timezone regions across the globe.
AST – Atlantic Standard Time
UTC-04:00Atlantic Standard Time (AST) is the time zone for the Canadian Atlantic provinces and the Caribbean, 4 hours behind UTC.
- •Puerto Rico uses AST year-round and does not observe DST.
- •AST is 1 hour ahead of EST.
- •Halifax, the capital of Nova Scotia, is the largest city in AST Canada.
CST – Central Standard Time
UTC-06:00Central Standard Time (CST) is the time zone for the central United States, Canada, and Mexico, 6 hours behind UTC.
- •CST covers 20 US states fully or partially.
- •Chicago and Houston are the two largest cities in the Central Time Zone.
- •Mexico City, one of the world's most populous cities, operates on CST.
- •CST is 1 hour behind EST and 2 hours ahead of PST.
Understanding the -2h Gap: AST vs CST
AST runs on Atlantic Standard Time (AST) at UTC-04:00. CST runs on Central Standard Time (CST) at UTC-06:00. That puts AST 2 hours behind CST — a difference of -2h at the current offsets.
In practice, when it is 9:00 AM in AST it is 7:00 AM in CST. Midnight in AST is 10:00 PM in CST. Neither zone observes daylight saving time, so the offset between them stays constant all year.
AST to CST time conversion table
| AST (AST) | CST (CST) | Day |
|---|---|---|
| 12:00 AM | 10:00 PM | previous day |
| 6:00 AM | 4:00 AM | same day |
| 7:00 AM | 5:00 AM | same day |
| 8:00 AM | 6:00 AM | same day |
| 9:00 AM | 7:00 AM | same day |
| 12:00 PM | 10:00 AM | same day |
| 3:00 PM | 1:00 PM | same day |
| 5:00 PM | 3:00 PM | same day |
| 6:00 PM | 4:00 PM | same day |
| 9:00 PM | 7:00 PM | same day |
Why people convert AST to CST time
- Scheduling a call from AST to CST: a 10:00 AM start in AST lands at 8:00 AM in CST, so you can confirm the slot without doing the arithmetic yourself.
- Finding shared working hours: both AST and CST are inside the 9-to-5 working day between 11:00 AM and 5:00 PM AST time (9:00 AM–3:00 PM CST). That is roughly 6 hours of usable overlap.
- Keeping family and friends in sync: knowing that 8:00 PM in AST is 6:00 PM in CST makes it easy to avoid calling at 3 AM.
- Always state the zone abbreviation, not just the hour. "3:00 PM AST" is unambiguous; "3 PM" across a -2h gap is not.
- Block 11:00 AM–5:00 PM AST as the recurring meeting window if you work primarily from AST and need CST colleagues present.
About AST (Atlantic Standard Time)
Atlantic Standard Time (AST) covers Canada's Atlantic provinces (Nova Scotia, New Brunswick, Prince Edward Island, and most of Labrador), as well as several Caribbean nations. Puerto Rico and the US Virgin Islands use AST year-round without daylight saving time. The Canadian provinces switch to Atlantic Daylight Time (ADT) in summer.
About CST (Central Standard Time)
Central Standard Time (CST) covers the central region of North America. It is the second most populous time zone in the US, including major cities like Chicago, Houston, and Dallas. CST is also used in Mexico City and much of Central America including Guatemala, Honduras, El Salvador, and Costa Rica. During summer, most of the US and Canada switch to Central Daylight Time (CDT, UTC-05:00), while Mexico and Central American countries generally remain on CST.
Best time to call between AST and CST
Both AST and CST sit inside the 9 AM – 5 PM working day between 11:00 AM–5:00 PM AST, which is 9:00 AM–3:00 PM CST. That gives roughly 6 hours of shared time — the safest window for a live call or meeting.
Business hours overlap
AST and CST share 6 hours of working-hours overlap (11:00 AM–5:00 PM AST), so scheduling a live meeting is straightforward.
AST is 2 hours behind CST (AST UTC-04:00 → CST UTC-06:00). The shared working window is 11:00 AM–5:00 PM AST. Remember to re-check around daylight-saving transitions.
🕐 Daylight Saving Time Info
AST
☀ Currently in DST
Standard: UTC-04:00 · DST: UTC-03:00
Clocks fall back on Sun, Nov 1, 2026
CST
☀ Currently in DST
Standard: UTC-06:00 · DST: UTC-05:00
Clocks fall back on Sun, Nov 1, 2026
Learn More About Time
Dive deeper into the fascinating world of timekeeping, time zones, and how they shape our global society:
Frequently Asked Questions
What is the time difference between AST and CST?
AST (AST, UTC-04:00) is 2 hours behind CST (CST, UTC-06:00). The gap is currently -2h.
How do I convert AST time to CST time?
Add -2h to AST local time. For example, 9:00 AM in AST is 7:00 AM in CST.
What time is it in CST right now?
CST uses CST at UTC-06:00. Use the live converter at the top of this page — it updates in real time and already accounts for the -2h offset from AST.
What is the best time to call CST from AST?
Call between 11:00 AM and 5:00 PM AST — that maps to 9:00 AM–3:00 PM CST and keeps both parties inside the working day.
Which is behind, AST or CST?
AST is 2 hours behind CST. When it is 12:00 PM in AST it is 10:00 AM in CST.
Does daylight saving time affect the AST–CST difference?
Neither zone observes daylight saving time, so the -2h offset between AST and CST is fixed all year.
Which other cities share AST's time zone?
AST also covers Halifax, San Juan, Santo Domingo, Caracas, La Paz, Fredericton, Charlottetown.
Which countries use AST, AST's zone?
AST is used in Canada (Atlantic provinces), Puerto Rico, US Virgin Islands, Dominican Republic, Venezuela, Bolivia, Barbados, Trinidad and Tobago.
Is there a day difference between AST and CST?
Not normally. The -2h gap only pushes the date over the previous day.
What is the time difference between AST and CST?
CST is -2h from AST.
What timezone is AST in?
AST operates on its local timezone.
What timezone is CST in?
CST operates on its local timezone.
Which countries use AST (Atlantic Standard Time)?
AST is used in Canada (Atlantic provinces), Puerto Rico, US Virgin Islands, Dominican Republic, Venezuela, Bolivia, and 2 more countries.
Does AST observe daylight saving time?
Yes, AST switches to ADT during summer months.
What are some interesting facts about AST?
Puerto Rico uses AST year-round and does not observe DST. AST is 1 hour ahead of EST.
Which cities are in the CST timezone?
Major cities in the CST timezone include Chicago, Houston, Dallas, San Antonio, Mexico City, Austin, Winnipeg, Memphis.
What is the UTC offset for CST?
Central Standard Time (CST) is at UTC-06:00. During daylight saving time, it shifts to CDT.
What should I know about the CST timezone?
CST covers 20 US states fully or partially. Chicago and Houston are the two largest cities in the Central Time Zone.
When is it midnight in AST, what time is it in CST?
When it is 12:00 AM (midnight) in AST (AST), it is -2h later in CST (CST).
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See every conversion from AST →·See every conversion from CST →