What is 10 days ago?
10 days is 1 week and 3 days, so it fell on the day of the week 3 days before today's.
Yesterday is 1 day ago, so count back from today without counting today itself.
10 days is 1 week and 3 days, so it fell on the day of the week 3 days before today's.
Yesterday is 1 day ago, so count back from today without counting today itself.