word choice - "which day is Friday" vs. "what day is Friday"

Thanks to:
"Which" vs. "what" — what's the difference and when should you use one or the other? I know that "what" can replace "which" in the examples below.
But which questions sound more more common?

• Which/what day is Friday? — It's the fifteenth.


• Which/what day is the first of November? Is it Saturday?



• Which/what month is the warmest in your city? — It's July.


• Which/what season is it now in your city? — It's summer.

Answer

For this, I have to turn to Google Ngrams:

What/Which day is

What/Which month is

What/Which year is

Based on the Ngram results, it seems clear that what is far more common today for all questions relating to dates (however, that wasn't always the case). This is also consistent with my preferred usage and experience, where I would hear what used probably 9/10 times.