what date

[Keralite]

Sentence :What date are you planning to leave for London?

Question : what or which should be used to refer a date

please help me out . Your help highly appreciated

[Charlie Bernstein]

Sentence :What date are you planning to leave for London?

Question : What or which should be used to refer a date. Which should I use here?

Please help me out. Your help highly appreciated.

When it's an open question, then what is correct:

I hear you're going to London. What date are you planning to leave?

When it's a choice of a limited number of dates, then which is correct:

I hear you're visiting foreign capitals on May 1, July 4, and July 14. Which date are you planning to leave for London?