[Weizsäcker's concept of time from the current viewpoint].

Carl Friedrich von Weizsäcker's concept of time is deeply based on the asymmetry between past and future, which he considers as a fundamental aspect of Nature. I review these ideas and their philosophical back ground and confront them with a presentation of the concept of time in modern physics. I argue that the observed irreversibility of our world can be understood from fundamental laws which are invariant under time reversal. I conclude with an outlook on the expected theory of quantum gravity.