At my previous work, we attempted to find the correlation between faulty code and the time of commit in the version control. Most bugs were written after 14:00. (And no: we didn't check-in all code at the end of the day).
I see similarities to another area where I have more experience: business meetings. I believe that most people are terrible at meetings held in the afternoon, either due to heavy lunch, or just because it's after 3pm and they are simply tired. A single meeting like this can cause great damage to the individuals and whole teams, measured in intangibles such as motivation, trust, momentum.