So... before we set off on our journey, let's check out where we're going - or rather where we want to go.
Chronotypes is a branch of sleep science. Repeat: science. This is not biorhythms or astrology; it won't help you to predict your future, correct your personality or resolve your love life. If that was what you were hoping, stop reading now. To get any value out of this pesky paradigm, we need to be crystal clear about where the value lies.
The science of chronotypes is based on biology (zoology, in fact): all animals tend to be either nocturnal or diurnal, and there are observable sub-groups within those categories. Humans are diurnal - mostly active during daylight, but that label hides significant variation. We can put that variation to good use, if we accept these two simple propositions
1. Humans who share the same sleep-behaviours will tend to form a little club: they'll encounter the same life-problems, and evolve the same set of possible solutions.
2. We can benefit from considering the set of solutions which correspond to our own little club.
There is no magic or mystery here: we are simply saving time by borrowing others' ideas.