I have a log file which records system usage on a server. I have a session start time and an end time. I would like to know how many concurrent users are accessing the system. Here is what I have done so far. I have created a new field for the duration of the session. Any transaction that does not last more than one second (i.e. 00:00:00) is ignored. I converted my dates from ISO format (yyyy-mm-dd hh:mm:ss to epoch time and am hoping to create a data structure to iterate over each enumeration in order to establish an intersection/concurrence. Logically, it seems like such a daunting task. So I wanted to discuss this case with the pros to find out how you all would address this problem. I am thinking of what would be the best way to implement this. For instance, most users would be connected for less than a couple of hours. So there is no reason to analyze data from the stack that is irrelevant! Any ideas or advise to guide this poor, lost monk? Thanks a lot.