"The nineteenth Saturday of the year is always in May."

[jardanovk]

Devetenáctá sobota v roce je vždy v MÁJI. ??

[endless_sleeper]

Not unless you're a 19th century Romantic poet.

I think the only expression where 'máj' is more suitable than 'květen' is 'první máj' (1st of May).

[JohnBraga1]

is ve květnu allowed?

[Jamie08MD]

It's not grammatically wrong, but we do not say that. I can't think of a situation where I'd prefer it over "v květnu".