The book exploreswhat types of chronometers came into use from the fifth century B. C. to late antiquity and how they measured time; when, where and why they became part of the societies of Greece and Rome; and by and for whom they were commissioned, designed and set up. For this purpose for the first time, some 500 chronometric instruments and their inscriptions from all over the classical world have been brought together to scrutinise questions such as form, typology, chronology, setting, function and context.