8:00 pm MST might be unsuitable for CT time zone
When planning a call between Mountain Standard Time and Central Time, you need to consider time difference between these time zones. MST is 2 hours behind of CT.
It is 8:00 pm in MST. This does not fall within the span of usual working time between 11:00 am and 6:00 pm in CT, but it still might be suitable to arrange a meeting, since it would be 10:00 pm in CT, which is between 7:00 am and 11:00 pm CT time.