MST stands for Mountain Standard Time, while MDT refers to Mountain Daylight Time. Mountain Daylight Time lags Coordinated Universal Time (UTC) by 6 hours, while Mountain Standard Time lags by 7 hours.
MDT is frequently listed as UTC – 6 hours or -0600, and MST as -0700. In the winter, many western states of the United States observe Mountain Standard Time, and in the summer, Mountain Daylight Time. In certain states, some portions of the state adhere to this pattern while others do not. MDT and MST are also utilised in portions of the western mountainous regions of Canada and Mexico.