Dienes & Perner's target article contains numerous but unsystematic references to the implicit or explicit knowledge of the temporal context of a known state of affairs such as may constitute the content of a propositional attitude. In this commentary, the forms of cognition that, according to D&P, require only implicit knowledge of time are contrasted with those for which explicit temporal knowledge is needed. It is suggested that the explicit representation of time may have been important in human evolution and that certain developmental disorders including autism may be (partly) caused by defective ability to represent time.