As an editor I have given up on setting deadlines for reviewers, asking them instead to set their own deadline themselves, in the hope that they are more likely to respect it then.
As a teacher this year I have let my TAs influence me and set most deadlines for assignments at midnight. Students at Brown reputedly go to bed at 2am on average, and "don't really get all they could from their life at Brown if they go to bed before midnight, since that's when things start happening". (Those "things" do not include lectures as far as I know.)
As a person, I am so glad that I am beyond the student stage and that most of my deadlines are now "soft" - indeed, I am chronically late, always, everywhere, and in everything. How ironical for me to penalize students for not respecting rules (such as turning reports in on time) that I would have the greatest difficulty following myself. Fortunately the TAs, who tend to be serious students with good self-discipline, are usually so convinced that it is right and just to set those rules and to enforce them, that I am swayed by their conviction.