10:00 am ET might be unsuitable for MDT time zone
When planning a call between Eastern Time and Mountain Daylight Time, you need to consider time difference between these time zones. ET is 2 hours ahead of MDT.
It is 10:00 am in ET. This does not fall within the span of usual working time between 9:00 am and 4:00 pm in MDT, but it still might be suitable to arrange a meeting, since it would be 8:00 am in MDT, which is between 7:00 am and 11:00 pm MDT time.