"a Martian colony would still need to care significantly about the seasons and time of day" Sure, in most if not all of the places future humans may come to in

"a Martian colony would still need to care significantly about the seasons and time of day" Sure, in most if not all of the places future humans may come to inhabit, the celestial bodies will obviously have a strong influence on their lives and so they'll have to care. But, as I see it, this is more like marking events in a tool-tracked independent time system instead of having the time system devised around what's happening with celestial bodies around them because they can't do any better.