Does timing of emails matter?
First, I don't think it makes much difference. Researchers deal with information, and a lot of that information is communicated through emails nowadays. So, most researchers I know are very careful about their emails and read them thoroughly. Especially if you write to people who know you, your name should be enough for them to read your email through anyway.

But, I can understand if you have an important announcement to make to a large list of people (who don't all know you personally), you may want to “micro-optimize” this. I have done it in the past: having a call-for-papers email ready on Saturday, and waiting ’til Monday afternoon (US time) to send it, thinking people who read it with a fresh mind, and not alongside the batch of “week-end email” that they might triage on Monday morning. (Some people stay connected during week-ends, of course, and for those it makes no matter.)