TLDR: Yes, but only to non-business emails.
It turned out weekends had excellent open rates for personal email addresses (@gmail, @yahoo, @hotmail, @outlook, etc) but low open rates for business emails (all other non-@gmail etc addresses).
So from now on we're sending marketing emails to businesses only on weekdays but to everyone else we're sending marketing emails on all days of the week, including Saturdays and Sundays.
Before this experiment we were sending marketing emails to everyone on all days of the week.
See you next time!