In summer, Jasper is on Mountain Daylight Time (MDT, UTC -6).
Beware! If you are coming to Jasper from British Columbia, you will be crossing a time zone, going from Pacific Daylight Time (PDT, UTC -7) to Mountain Daylight Time (MDT, UTC -6). This means that you will lose an hour as you cross the provincial border (only 25km west of Jasper) from British Columbia to Alberta. Please take this into consideration when planning your trip.