Résumé : We consider the problem of synchronizing clocks in synchronous systems prone to transient and dynamic process failures, i.e., we consider systems where all processes may alternate correct and Byzantine behaviors. We propose a clock synchronization algorithm based on periodical resynchronizations which is based on the assumption that no more than f < n/3 processes (with n the number of processors in the system) are simultaneously faulty. Both, accuracy (clocks being within a linear envelope of real-time) and precision (maximum deviation between clocks) perpetually hold for processes which sufficiently long follow their algorithm. We provide expressions for both the recovery time and the failure turn-over rates. Both expressions are independent of f, and are less than the time needed to execute 3 resynchronizations.