What is the time difference between AST and MST?

MST is 3h 0m behind AST. AST is UTC-4 and MST is UTC-7.

Does AST change for daylight saving time?

AST is a fixed offset of UTC-4 and does not itself change for daylight saving time.

MST is 3h 0m behind AST. When it's 12:00 PM AST, it's 9:00 AM MST.

From

AST · UTC-4

12:09:47AM

Atlantic Standard Time

MST · UTC-7

9:09:47PM

Mountain Standard Time

9:00 AM AST=6:00 AM MST

12:00 PM AST=9:00 AM MST

5:00 PM AST=2:00 PM MST

Shaded rows are within standard working hours (8am–6pm) on both sides.

MST (UTC−7) is the standard-time offset; most of the US Mountain region uses MDT (UTC−6) in summer.

What is the time difference between AST and MST?: MST is 3h 0m behind AST. AST is UTC-4 and MST is UTC-7.
What is 12:00 PM AST in MST?: 12:00 PM AST is 9:00 AM MST.
Does AST change for daylight saving time?: AST is a fixed offset of UTC-4 and does not itself change for daylight saving time.