You can set up a Date/time AB test in an email send program OOTB to see what date/time works best for your audience. Also, in the email performance report, there are columns for the first and last activity that refer to the first time someone had a Delivered, Clicked, Opened, or Unsubscribed activity and the most recent time one of those was logged, respectively. Also, if you've RCE included in your subscription, then you could effortlessly go wild with analysis of your past email engagement data (see sample chart below):

You'd probably know, but FYR email clicks and opens are not dead-drop accurate metrics to make big content decisions because of activities from the email scanners.