The water-clock is called a clepsydra in the text, I believe. The well-to-do seem to have them. The dingus in the autarch's bedroom has been seen by nobody talking.
There are also sundials. Even a pocket sundial. Candles marked off with the watches.
Note that the "watches" are probably seasonally adjusted (and I don't mean "Spring forward, Fall back"--or do I?). So the watches of the night are literally longer (rather than being more numerous) in the winter than in the summer (the Japanese used to reckon time this way). But maybe not.
If they are, however, then a modern clock such as we use would seem to them to be isochronal, since the watches of day and night are equal to each other and unvarying through the seasons. Our measure and concept of time is quite mechanical and relatively recent.
=mantis=