Highlighted rows fall within 09:00–18:00 in both places: 7 shared working hours.
How many hours is CST behind AST?
As abbreviations, AST is always 2 hours ahead of CST: CST is UTC−6 and AST is UTC−4. To convert, add 2 hours.
When the CST to AST time difference changes
For most of the year AST is 1 hour ahead of CST. From 1 November to 31 December 2026, AST is 2 hours ahead of CST instead, because the two places change their clocks on different dates. Meetings booked by the usual gap land an hour off in those weeks.
Dates
AST vs CST
Length
1 November 2026 to 31 December 2026
2 hours ahead
61 days
1 January 2027 to 13 March 2027
2 hours ahead
72 days
14 March 2027 to 6 November 2027
1 hour ahead
238 days
7 November 2027 to 31 December 2027
2 hours ahead
55 days
Calling hours for CST and AST
When AST is 1 hour ahead of CST: 7 shared office hours, 09:00 to 16:00 in CST (10:00 to 17:00 in AST).
When AST is 2 hours ahead of CST: 6 shared office hours, 09:00 to 15:00 in CST (11:00 to 17:00 in AST).
Frequently asked questions about CST and AST time
How many hours ahead is AST of CST?
AST (UTC−4) is 2 hours ahead of CST (UTC−6).
Does the time difference between CST and AST change?
Yes. It is usually 1 hour ahead, but changes when one side moves its clocks: 2 hours ahead from 1 November to 31 December 2026; 2 hours ahead from 1 January to 13 March 2027.