9:00 pm EST might be unsuitable for CST time zone
When planning a call between Eastern Standard Time and Central Standard Time, you need to consider time difference between these time zones. EST is 1 hour ahead of CST.
It is 9:00 pm in EST. This does not fall within the span of usual working time between 9:00 am and 5:00 pm in CST, but it still might be suitable to arrange a meeting, since it would be 8:00 pm in CST, which is between 7:00 am and 11:00 pm CST time.