What is 100 days ago?
100 days is 14 weeks and 2 days, so it fell on the day of the week 2 days before today's.
Yesterday is 1 day ago, so count back from today without counting today itself.
100 days is 14 weeks and 2 days, so it fell on the day of the week 2 days before today's.
Yesterday is 1 day ago, so count back from today without counting today itself.