My band's RSS feed stopped being valid. It took me a while to see what was breaking. Something with my date format was causing things to not validate. Once I spotted it, things started validating.

I had this for my date which seems correct...

Mon, 30 October 2023 08:00:00 +0900

Turns out that you need to use the short version of the month...

Wed, 02 Oct 2002 08:00:00 +0900

So use "Oct" and not "October".