The person who asks for a deadline may be trying to manage more than your task.

A request for a date is usually not impatience. The person asking has other pieces that depend on yours, and without a time they cannot arrange anything around it, so the question is about their own planning rather than a judgment on your speed. Vagueness feels generous to give and is expensive to receive.

When someone asks when, resist the instinct to keep it open. Offer a date you can actually meet, even a conservative one, and say you will tell them early if it changes. A date that turns out to be wrong but was honestly given is still far more useful than no date at all.