AST to CST Time Converter
CST is 2 hours behind AST. Atlantic Canada and the Caribbean are currently on ADT (UTC-3:00), and The US Central states are currently on CDT (UTC-5:00).
Best Time to Call Between AST and CST
Both zones are inside normal business hours between 11:00 AM and 5:00 PM AST — that's 9:00 AM to 3:00 PM CST. That's a 6-hour window.
both at work AST only CST only neither — hours along the strip are AST.
Common Times Converted
AST on the left, CST on the right.
AST to CST: Full 24-Hour Conversion Table
Shaded rows are working hours; the darker shade marks the hours when both zones are at work.
| AST | CST | Working hours |
|---|---|---|
| 12:00 AM | 10:00 PM prev day | — |
| 1:00 AM | 11:00 PM prev day | — |
| 2:00 AM | 12:00 AM | — |
| 3:00 AM | 1:00 AM | — |
| 4:00 AM | 2:00 AM | — |
| 5:00 AM | 3:00 AM | — |
| 6:00 AM | 4:00 AM | — |
| 7:00 AM | 5:00 AM | — |
| 8:00 AM | 6:00 AM | — |
| 9:00 AM | 7:00 AM | AST only |
| 10:00 AM | 8:00 AM | AST only |
| 11:00 AM | 9:00 AM | Both zones |
| 12:00 PM | 10:00 AM | Both zones |
| 1:00 PM | 11:00 AM | Both zones |
| 2:00 PM | 12:00 PM | Both zones |
| 3:00 PM | 1:00 PM | Both zones |
| 4:00 PM | 2:00 PM | Both zones |
| 5:00 PM | 3:00 PM | CST only |
| 6:00 PM | 4:00 PM | CST only |
| 7:00 PM | 5:00 PM | — |
| 8:00 PM | 6:00 PM | — |
| 9:00 PM | 7:00 PM | — |
| 10:00 PM | 8:00 PM | — |
| 11:00 PM | 9:00 PM | — |
What AST and CST Actually Are
AST — Atlantic Standard Time
Halifax, San Juan, Santo Domingo, Bermuda. Standing at UTC-4:00 as written, and the region does change its clocks, so its live offset moves by an hour twice a year. The next change is on Sunday, November 1, 2026, to AST. AST also stands for Arabia Standard Time (UTC+3), used in Saudi Arabia, Iraq and Kuwait.
Atlantic Standard Time is the only North American zone whose name is more commonly associated, worldwide, with a completely different zone — Arabia Standard Time.
CST — Central Standard Time
Chicago, Houston, Dallas, Mexico City, Winnipeg. Standing at UTC-6:00 as written, and the region does change its clocks, so its live offset moves by an hour twice a year. The next change is on Sunday, November 1, 2026, to CST. CST also stands for China Standard Time (UTC+8) and Cuba Standard Time (UTC-5). This page covers the North American one.
Saskatchewan sits inside the Central zone but never changes its clocks, so it matches CST in winter and its neighbors' MDT in summer.
What This Means in Practice
Both sides change clocks, on different dates
Both regions observe daylight saving but do not switch on the same day, so for a week or two each spring and fall the gap between them is an hour different from the rest of the year. Those short windows are where recurring invitations quietly break.
Close enough to share a working day
At only 2 hours apart, the two working days overlap almost completely. Scheduling is barely constrained by the difference.
Major Cities in Each Zone
Cities on AST
Cities on CST
Frequently Asked Questions
What is the time difference between AST and CST?
CST is 2 hours behind AST.
What is 9:00 AM AST in CST?
9:00 AM AST is 7:00 AM CST.
What are the best hours to schedule a call between AST and CST?
Between 11:00 AM and 5:00 PM AST, which is 9:00 AM to 3:00 PM CST. Both sides are inside normal business hours through that window.
Does the difference between AST and CST change during the year?
Yes. Both regions observe daylight saving, and they do not switch on the same dates, so the gap shifts by an hour at least twice a year. The next clock change is on Sunday, November 1, 2026.
Does AST always mean Atlantic Standard Time?
AST also stands for Arabia Standard Time (UTC+3), used in Saudi Arabia, Iraq and Kuwait.
Does CST always mean Central Standard Time?
CST also stands for China Standard Time (UTC+8) and Cuba Standard Time (UTC-5). This page covers the North American one.