The Astronomical Clock at Prague was built in 1410, with later additions, and is beautifully preserved and fully functioning. It shows time “by the sun,” as marked on an astrolabial dial, and also time “metronomically,” with an hand going round once every twenty-four hours. After explaining the (admirable) features of the astronomical clock, we list the sequence of departures from scientific sensibility that gave rise to the (not so admirable) modern clock as we know it now.