I was going through the US border control in an airport a couple days ago and the customs officer asked me a question that was kind unexpected. I don't remember the question exactly but it definitely was past perfect tense or future perfect tense because it contained something like "how long have you stayed in the US" in the sentence. I assumed he was asking about the duration of my stay in the states so I answered I would stay there for 3 days and he accepted that answer.
But I was really confused when he asked that question because I was expecting something like"how long will you stay" and didn't anticipate it involving "have" in it. So my question is, can you guys think of any sentences that can be used to ask for the duration of the stay while containing "have you" in it?