There's a first Sunday in every month

Used to mean just because something has never happened doesn't mean it won't.

I've never been out on a date with a bald man.
There's a first Sunday in every month.

there's a first Sunday in every month

Just because something has never happened, doesn't mean it won't ever happen.

" I've never and will never kiss a man with a mustache."
"There's a first Sunday in every month."