6:00 pm PT might be unsuitable for MDT time zone
When planning a call between Pacific Time and Mountain Daylight Time, you need to consider time difference between these time zones. PT is 1 hour behind of MDT.
It is 6:00 pm in PT. This does not fall within the span of usual working time between 10:00 am and 6:00 pm in MDT, but it still might be suitable to arrange a meeting, since it would be 7:00 pm in MDT, which is between 7:00 am and 11:00 pm MDT time.