What / When> is the deadline?


Senior Member
Dear all,

(What / When) is the deadline to hand in the report?
Next monday.

I made up the sentences. To me, 'when is the deadline...' makes sense but there're many 'what's the deadline...' version on the Internet.
I would appreciate if anyone would give some explanation about the choice of what or when?
  • "When" asks specifically for a time, so it is correct.

    "What" can ask for anything, but when it is used about a deadline - which is a time - it can only refer to a time, so it is correct also.

    That is why you can use either one.
    How do you ask this question when it has a date?

    - Is the deadline March 8th?