It's pretty straight-forward. Just pick any times that are formatted per Excel's time "13:30" format, and that's what my times look like. Example:

4:00
4:11
4:17
4:20
4:25
etc
etc

Expected results would be as I posted in the example above. So, in the above example, the most active 15 minute period might be 4:37-4:52, to use my previous example. However, I should be able to change that "15 minute" variable (call it "X") to any number of minutes, like "40", as in "what is the most active 40 minute period?" (has the greatest count of times) or most frequent data from column A.