Horology is the scientific study of time. Specifically, horology involves the measurement of time and the making of clocks.
You need a small leap of imagination to see hour in horology, but if you do, you've pretty much nailed the meaning: it refers to the study of time and the art of making timepieces. In horology, time is studied scientifically, just as a geologist studies the earth and a biologist studies life. Horology is very practical, since it involves the design and construction of clocks, watches, and other devices for measuring time. Someone who studies horology is a horologist.