In a large class of hard-real-time control applications, components execute concurrently on distributed nodes and must coordinate, under timing constraints, to perform the control task. As such, they perform a type of atomic commitment. Traditional atomic commitment differs, however, because there are no timing constraints; agreement is eventual. We therefore define timed atomic commitment (TAC) which requires the processes to be functionally consistent, but allows the outcome to include an exceptional state, indicating that timing constraints have been violated. We then present centralized and decentralized protocols to implement TAC and a high-level language construct that facilitates its use in distributed real-time programming.