Most other e-mail marketing clients have the option, to spilt test based on time.
So you can send out your mail to 50% of your list in the afternoon, and 50% in the evening, and check what gives the best opening and click rates and learn from that. Or just send to 2x10% and use the winning stategy on the rest the following day.
I see that several users have been asking for this the last 3 years. Why is this not possible in Click Dimensions?