[SiempreViernes]

Those are important events in the day, but they don't serve as a basis for defining time.

When does work start? Well, it starts when the hands on the clock points just so, there really isn't any more fundamental definition. But clocks are tools for measuring time, they don't define it.

If your clock slows nothing particular happens to other clocks, and time marches on unslowed. But sunset will bring night whether you notice it or not, and that's a pretty definite marker of the passage of time.