Is 'from when to when?' or 'from what time to what time?' proper/natural English? Would their usage come up in a conversation between native speakers as a super concise way of asking when something starts and when it will end? For example:
A: I will be going away on a holiday to Paris.
B: Oh that's nice. From when to when?
If it's not idiomatic, how else I can express the same query without being too wordy? What are some alternative phrases, both formal and informal?
Many thanks in advance.