Clocks Through History;"Water clocks have been developed since as early as 4000 BC. Greek astronomer Andronicus of Cyrrhus supervised the construction of the Tower of the Winds in Athens in the 1st century BC. Greek and Roman civilizations are credited for initially advancing water clock design to include complex gearing, which was connected to fanciful automata and also resulted in improved accuracy. These advances were passed on through Byzantium and Islamic times, eventually making their way back to Europe. Independently, the Chinese developed their own advanced water clocks in 725 AD. Islamic civilization is credited with advancing the accuracy of clocks with elaborate engineering. In 797 AD the Abbasid caliph of Baghdad, Harun Al-Rashid, presented Charlemagne with an Asian elephant named Abul-Abbas together with a particularly elaborate example of a water clock. Pope Sylvester II introduced clocks to northern and western Europe around 1000AD". Star Trek time is by "stardate".