I read a great article about when to tweet by Andrew Phelps who was basically reaping a presentation from Dan Zarrella so for those of you with  a short attention span like me here is my summary of Andrew's article that summarizes Dan's presentation.

When and how often to tweet - A few key takeaways:
  • If your goal is more followers Tweet More: Twitter’s A-listers — those with the most followers — tweet an average of 22 times a day
  • If your goal is more visitors to your site tweet less - accounts that share two or more links an hour show a dramatically lower clickthrough rate than those who share no more than one
  • The trick is to reach people when the noise of the crowd has died down. - That time is the afternoon when news sites are slower and on the weekend
  • Retweet activity is highest late in the work day, between 2 and 5 p.m.
  • Check out TweetWhen to find out what time of day is the best time to tweet for you. Turns out my prime time is Thursdays at 10PM- I guess I have some late night followers @jonballard
  • It's ok to tweet the same links two or three times a day- change up the verbiage and let it rip.

Here are Dan's Power Point Slides: The Science of Timing