What do you mean, what knowing the day of week a date is useful for ?
"3 Nov" is ambiguous, it could mean 2020-11-03 or 2021-11-03, or any other year. And by the way, "3 Nov 21" is also ambiguous, it could be 2021-11-03 or 1921-11-03. Lots of stuff happened in 1921.
What do you mean, what knowing the day of week a date is useful for ?
"3 Nov" is ambiguous, it could mean 2020-11-03 or 2021-11-03, or any other year. And by the way, "3 Nov 21" is also ambiguous, it could be 2021-11-03 or 1921-11-03. Lots of stuff happened in 1921.