I used to have data culled from my AMS ads that indicated my readers were clicking in late afternoon and evening weekdays and similar times on weekends. I don't recall there being one weekday better than another, but I have been left with the impression that weekends are better.
I understand trad pubs release on Tuesdays, but as to the best day of the week to sell, I have no clue.
You're right that the disruption of traditional commuting to work (yay!) may have changed browsing habits. I assume most people have a certain time of day, or several times per day, when they check newsletters and info sites, and Facebook, and so on. People who tweet are on all day, though, and yet Twitter famously does not move books. So...nothing clear to give you.