CST to AST
+2hCST
CSTSOURCEAST
ASTGreen rows indicate typical business hours (9 AM - 5 PM)
CST and AST on the World Map
The map below highlights the CST (Central Standard Time) and AST (Atlantic Standard Time) timezone regions across the globe.
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.
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 vs AST: Offsets, DST and Best Call Times
CST runs on Central Standard Time (CST) at UTC-06:00. AST runs on Atlantic Standard Time (AST) at UTC-04:00. That puts CST 2 hours ahead of AST — a difference of +2h at the current offsets.
In practice, when it is 9:00 AM in CST it is 11:00 AM in AST. Midnight in CST is 2:00 AM in AST. Neither zone observes daylight saving time, so the offset between them stays constant all year.
CST to AST time conversion table
| CST (CST) | AST (AST) | Day |
|---|---|---|
| 12:00 AM | 2:00 AM | same day |
| 6:00 AM | 8:00 AM | same day |
| 7:00 AM | 9:00 AM | same day |
| 8:00 AM | 10:00 AM | same day |
| 9:00 AM | 11:00 AM | same day |
| 12:00 PM | 2:00 PM | same day |
| 3:00 PM | 5:00 PM | same day |
| 5:00 PM | 7:00 PM | same day |
| 6:00 PM | 8:00 PM | same day |
| 9:00 PM | 11:00 PM | same day |
Why people convert CST to AST time
- Scheduling a call from CST to AST: a 10:00 AM start in CST lands at 12:00 PM in AST, so you can confirm the slot without doing the arithmetic yourself.
- Finding shared working hours: both CST and AST are inside the 9-to-5 working day between 9:00 AM and 3:00 PM CST time (11:00 AM–5:00 PM AST). That is roughly 6 hours of usable overlap.
- Coordinating a CST-based team with AST contacts: quoting times in the other side's local clock — not your own — removes the single biggest source of missed meetings.
- Always state the zone abbreviation, not just the hour. "3:00 PM CST" is unambiguous; "3 PM" across a +2h gap is not.
- Block 9:00 AM–3:00 PM CST as the recurring meeting window if you work primarily from CST and need AST colleagues present.
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.
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.
Best time to call between CST and AST
Both CST and AST sit inside the 9 AM – 5 PM working day between 9:00 AM–3:00 PM CST, which is 11:00 AM–5:00 PM AST. That gives roughly 6 hours of shared time — the safest window for a live call or meeting.
Business hours overlap
CST and AST share 6 hours of working-hours overlap (9:00 AM–3:00 PM CST), so scheduling a live meeting is straightforward.
CST is 2 hours ahead of AST (CST UTC-06:00 → AST UTC-04:00). The shared working window is 9:00 AM–3:00 PM CST. Remember to re-check around daylight-saving transitions.
🕐 Daylight Saving Time Info
CST
☀ Currently in DST
Standard: UTC-06:00 · DST: UTC-05:00
Clocks fall back on Sun, Nov 1, 2026
AST
☀ Currently in DST
Standard: UTC-04:00 · DST: UTC-03:00
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 CST and AST?
CST (CST, UTC-06:00) is 2 hours ahead of AST (AST, UTC-04:00). The gap is currently +2h.
How do I convert CST time to AST time?
Add +2h to CST local time. For example, 9:00 AM in CST is 11:00 AM in AST.
What time is it in AST right now?
AST uses AST at UTC-04:00. Use the live converter at the top of this page — it updates in real time and already accounts for the +2h offset from CST.
What is the best time to call AST from CST?
Call between 9:00 AM and 3:00 PM CST — that maps to 11:00 AM–5:00 PM AST and keeps both parties inside the working day.
Which is ahead, CST or AST?
CST is 2 hours ahead of AST. When it is 12:00 PM in CST it is 2:00 PM in AST.
Does daylight saving time affect the CST–AST difference?
Neither zone observes daylight saving time, so the +2h offset between CST and AST is fixed all year.
Which other cities share CST's time zone?
CST also covers Chicago, Houston, Dallas, San Antonio, Mexico City, Austin, Winnipeg, Memphis and 6 more.
Which countries use CST, CST's zone?
CST is used in United States (Central), Canada (Manitoba, Saskatchewan), Mexico, Guatemala, Honduras, El Salvador, Costa Rica, Nicaragua and 1 more.
Is there a day difference between CST and AST?
Not normally. The +2h gap only pushes the date over for late-evening times.
What is the time difference between CST and AST?
AST is +2h from CST.
What timezone is CST in?
CST operates on its local timezone.
What timezone is AST in?
AST operates on its local timezone.
Which countries use CST (Central Standard Time)?
CST is used in United States (Central), Canada (Manitoba, Saskatchewan), Mexico, Guatemala, Honduras, El Salvador, and 3 more countries.
Does CST observe daylight saving time?
Yes, CST switches to CDT during summer months.
What are some interesting facts about CST?
CST covers 20 US states fully or partially. Chicago and Houston are the two largest cities in the Central Time Zone.
Which cities are in the AST timezone?
Major cities in the AST timezone include Halifax, San Juan, Santo Domingo, Caracas, La Paz, Fredericton, Charlottetown.
What is the UTC offset for AST?
Atlantic Standard Time (AST) is at UTC-04:00. During daylight saving time, it shifts to ADT.
What should I know about the AST timezone?
Puerto Rico uses AST year-round and does not observe DST. AST is 1 hour ahead of EST.
When is it midnight in CST, what time is it in AST?
When it is 12:00 AM (midnight) in CST (CST), it is +2h later in AST (AST).
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See every conversion from CST →·See every conversion from AST →