This article reviews the evidence that living systems at all levels, including cells, organs, organisms, groups, organizations, communities, societies, and supranational systems, have an information-processing system, the timer. The timer consists of one or more oscillators known as clocks or pacemakers, the phase of which can be reset. They measure duration or order in time or underlie rhythms of various sorts. The timer subsystem synchronizes internal processes of the system and coordinates the system with its environment. By 1965, 19 matter-energy and information processing subsystems were identified in living systems theory. Based on scientific evidence accumulated particularly in recent years, the timer is now recognized as an information processing subsystem, the 20th subsystem, which carries out an essential life process.