Highlighted rows fall within 09:00–18:00 in both places: 5 shared working hours.
How many hours is MST behind ART?
As abbreviations, ART is always 4 hours ahead of MST: MST is UTC−7 and ART is UTC−3. To convert, add 4 hours.
When the MST to ART time difference changes
For most of the year ART is 3 hours ahead of MST. From 1 November to 31 December 2026, ART is 4 hours ahead of MST 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
ART vs MST
Length
1 November 2026 to 31 December 2026
4 hours ahead
61 days
1 January 2027 to 13 March 2027
4 hours ahead
72 days
14 March 2027 to 6 November 2027
3 hours ahead
238 days
7 November 2027 to 31 December 2027
4 hours ahead
55 days
Calling hours for MST and ART
When ART is 3 hours ahead of MST: 5 shared office hours, 09:00 to 14:00 in MST (12:00 to 17:00 in ART).
When ART is 4 hours ahead of MST: 4 shared office hours, 09:00 to 13:00 in MST (13:00 to 17:00 in ART).
Frequently asked questions about MST and ART time
How many hours ahead is ART of MST?
ART (UTC−3) is 4 hours ahead of MST (UTC−7).
Does the time difference between MST and ART change?
Yes. It is usually 3 hours ahead, but changes when one side moves its clocks: 4 hours ahead from 1 November to 31 December 2026; 4 hours ahead from 1 January to 13 March 2027.