They say Déjà vu is just a sensory familiarity, or a glitch in The Matrix. But those time jumping know-it-alls can tell us the truth weve been here before. See a face you recognize? Having a conversation you feel youve already had? Thats because you do and you have. Time travelling usually requires the traveller to have at least two encounters with the same individual, and prophetically impart wisdom to them. One result of meeting younger or past people is that they seldom remember you. So anything you do tell them rarely holds, and when you do meet them again in the distant future you will be dismissed as that elusive little flutter with the French phrasing. Most likely to say: You wont remember this, but CASE STUDIES: The Jacket, Groundhog Day