Can I apply Standard Deviation and IQR on daily work hours?


I'm wondering if we could apply standard deviation or IQR on our daily log on time?
I have a dataset with many machine ID that has many log in records for entire month.
I have removed the weekend data and left with log in data of over 1000 machines.

From the dataset, each machines has several logins in a day at different time. Taking an example of a machine, if I group by time and count the logins for the entire month, I will have login from at different times from 0000hrs to 2359hrs.

If the 0th percentile is 8am, the 100th percentile is 1730pm. Between these time, there are over 300 logins. I want to use these data to detect abnormal logs outside of 2 standard deviation. The mean could be maybe 1300pm. 2 SD may be 4hrs. The lower 2SD is 9am and upper 2SD is 1900pm.

Does this make any sense?