Earliness–tardiness criteria with distinct due dates usually induce NP-complete problems. Researchers have focused on particular cases like the timing problem, which is to look for the optimal schedule when the jobs sequence is already known. These timing algorithms are very useful since they can be used in more complex procedures. In the first part of this paper we provide the most efficient and fairly general algorithm to solve the one-machine timing problem. It is then adapted to a permutation flow shop problem.