Earlier quoted context omitted.
It's not about the length. It might be a perfect day for them, it's not the point. It's about the fact that you have to use 100 ksec instead of a "day". "Each day" is not the same thing as "each 100 ksecs", since the latter has much more implicit precision. So, practically speaking, your either have a concept of 1-day cycle (because of sleep, sun, or whatever — doesn't matter why they need it and how long must it be…
It’s so ridiculous that you have invented something completely unlike what is in the book. They don’t try to force anything to line up to powers of ten, they haven’t changed the length of the second, and they have wearable computers to eliminate any and all annoyances associated with communicating long timestamps. Although the book only hints at how things are implemented, the result is apparently really flexible. Th…
Sure, you can just set up a timer which would alert you at some arbitrary moment in the future that it is time to do something. It's how computers do it (if we forget about leap seconds and such). But the point of the calendar and the clock with sane time units (like a minute and an hour) is to keep the frequency and time of your dentist appointments, train schedules and vacations somewhat workable in your head. Which would be much less fun to do in Unix-time.