I understand (and please correct me if I am wrong) that 'soon' simply means 'a short period of time'. With that in mind, I would like to relate a conversation I recently had with my wife.
"I gave the baby her medicine just before you came home," my wife told me. "How soon before I came home, did you give the baby her medicine?" I asked her in response.
What I meant to ask was, what was that short period of time which had elapsed between these two events. According to her, this is incorrect because 'soon' can only refer to something which will occur in the future.
Which one of us is correct?