In the graph below you see the time zone difference between Greenwich Mean Time and Mountain Standard Time. Drag the bubble to adjust the time and to see the corresponding time in the other time zone.
Greenwich Mean Time is the time zone of the 0 meridian, located in London, United Kingdom, including cities like London, Lisbon and Dublin (in the winter). Mountain Standard Time is the time zone of the US and Canadian states around the Rocky Mountains when observing daylight saving time in the sum, with places like Edmonton, Calgary, Denver and Salt Lake City.
Usually it is preferable to schedule meetings in the late afternoon for the person in GMT and before lunch for the person in MST.
GMT, or Greenwich Mean Time, is the zero when it comes to time zones – they are all counted from the zero meridian that runs through the village of Greenwich.
While both the UK and Portugal are officially on GMT you need to pay attention to whether they are actually observing it or are using their own. Britain in the summer for example use British Summer Time – which is different than GMT.
London, Lisbon, Dublin, Edinburgh
GMT does not observe DST as it is the zero hour time zone – it never changes.
Mountain Standard Time is observed in the Western part of central US and Canada, as well as the North West corner of Mexico. It is 7 hours behind UTC and turns into MDT in the summer. The name Mountain Time comes from it covering the Rocky Mountains in Western United States. In Mexico, this time zone is known as Zona Pacifico (Pacific Zone).
Mountain Time is observed in parts of Canada, the US and Mexico. The only province in Canada to be fully covered by MST is Alberta whereas other provinces like British Columbia and Northwest Territories are split between MST and PST.
In the US, Arizona, Colorado, Montana, Utah and Wyoming are all observing Mountain Time but there is also a bunch where part of the state observe MST and part another time zone, like CST or PST.
In Mexico, it is only the states in the north western corner of the country, including Baja California, Sinaloa and Chihuahua that observe MST.
The largest city observing MST is Phoenix, followed by Denver and El Paso/Juarez.
Aside from Arizona and the Mexican state of Sonora, all other locations do observe DST, turning MST into MDT – Mountain Daylight Time. Given this, and the fact that not entire states observe the same time zone, it is always recommended to use a good time zone converter to convert specific locations’ times.