As an experiment, consider if we get rid of both the clock and the calendar, leaving us only with Unix time (which is utterly incomprehensible without a calendar or clock reference).
Timers would still work. Actions would then be more ad-hoc. The simple change would likely lower stress tenfold, and this is what can be measured.
How then would appointments work? Day offsets (from 0 to 2) would still easily work. People wanting to come in to see a specialist would just have to call/contact, then come in at any time of the day. Some would come in earlier in the day, and some would come in later in the day, somewhere between sunrise and sunset, and things would work out.
Everything would likely be slowed down in the immediate sense, but would this be so bad? Odds are that no; it would probably add much to happiness, and perhaps become more sustainable.
How would a big passenger airplane even depart? It wouldn't, and that's okay. Cargo planes and other dedicated airplanes would remain unaffected because they can depart when there is sufficient mass.
It would be like a return to old times, maybe to an extreme version of Italy. The early chaos, if managed aptly, would soon manifest as a longer and healthier life.
