From
AST / ADT
Time Converter
AST to MST Time Converter
Convert Atlantic Time to Mountain Time with a live clock and clean permalinks.
To
MST / MDT
When it is 7:30 AM in Atlantic Time, it is 4:30 AM in Mountain Time.
AST to MST at a glance
Mountain Time is 3 hours behind Atlantic Time. If someone gives you a time in Atlantic Time, move the clock by 3 hours to read it in Mountain Time. A 9:00 AM start in Halifax becomes 6:00 AM in Denver.
What Atlantic Time covers
Atlantic Time is used in eastern Canada and parts of the Caribbean. Halifax is a common city reference for it. It matters when scheduling across North America and island markets farther east.
What Mountain Time covers
Mountain Time is used across the US and Canada in cities such as Denver and Calgary. It is useful when you work with logistics, field teams, or regional teams across the western half of North America.
Quick answers
What is the time difference between AST and MST?
Mountain Time is 3 hours behind Atlantic Time.
What happens to a 3:00 PM meeting in AST?
It lands at 12:00 PM in MST.
Does daylight saving time matter for AST to MST?
Atlantic Time and Mountain Time are shown using the offsets that are active right now, so the result already reflects any daylight saving change in effect today.