8:00 pm CT might be unsuitable for ET time zone
When planning a call between Central Time and Eastern Time, you need to consider time difference between these time zones. CT is 1 hour behind of ET.
It is 8:00 pm in CT. This does not fall within the span of usual working time between 10:00 am and 6:00 pm in ET, but it still might be suitable to arrange a meeting, since it would be 9:00 pm in ET, which is between 7:00 am and 11:00 pm ET time.