n this chapterIexploreGraeco-Roman techniques of, and attitudes towards,time measurement,from the twin perspectivesofeverydaylife andmedicine. Isurvey literary and archaeological evidence for the twomain available technol-ogies of timemeasurement,sundials and water-clocks, and consider what thisevidence tells us about their differential accessibility and context of use, andabout Roman attitudes to dailyorhourlytime organization.Ithen proceed to ex-amine further some literary,and, in more detail, some medical texts which shedlight on ancient attitudesto time management and the division of the day; on theimportance of, and relationship between, the two forms of time measurement,aswell as the relationship of seasonal to equinoctial hours; and on the balance ofwork and leisure, in particular exercise, activities within such dailytime divisions. An obelisk towered highoverthe Campus Martius in Rome. Built in 10/9 BCE, thehorologiumof the emperorAugustus cast its shadow overalong stretch of thelow-lying area, whereametal line and markingshad been laid in the ground.It was itself visible fromagreat distance and complemented two other greatAu-gustan edifices in the samearea: the MausoleumAugusti and the AraPacis.(Seefigures1and 2.)The line on the groundrandue northfrom the obelisk:ameri-dian, which the shadow hit at noon each day. The markingsalong its length in-dicated different dates, and these would be hit by the shadow at noon on suc-cessive days,asitgrew longer or shorter in the course of theyear.Prominentlyplaced abovethe forum, meanwhile–the centreofboth legaland commercial activity in the city–wereone or two sundials, visiblydividingthe passing time of daylightinto twelve equal units, which, by the late secondcentury CE, the date of thetextswhich we shall focus on in this chapter,hadstood therefor more than threehundredyears. Other,equallypubliclyvisible,sundials werefeatures of cities throughout the Graeco-Roman world.Afew steps from those public sundials, the ancientvisitor to the forum–ifby chance business affairs took him into theBasilicaAemilia etFulvia–wouldfind an equallyvenerable instrument of time measurement,awater-clock orclepsydra,placed there in theyear 159 BCE, and dividing the dayinto(probably)half hours.