The standard format for contest logging is Cabrillo, which permits only one item for time.
Therefore the contest adjudicators will never see more than one time in a contest log, so they will never have information to decide the matter, and they will not dig into that sort of detail. Contesting software generally logs the time at the end of the QSO, and only that, so if you have trouble deciding the start of a QSO, it is not a problem. I guess it is easier to agree when the QSO ended. Log checking software is often set to accept up to five minutes time difference between your logged time and your QSO partners logged time, so if you and your QSO partner agree and log approximately the same time, the case is settled. If the time difference is more than the permitted time difference, the QSO will not count for either of you, and the contest adjudicators will do anything more about it..
