Very dependable and memorizable thing, the sunrise.
Uh, yeah? Because it defines your circadian rhythm?
Ah yes, clock time. That things that never ever changes depending on the time of year or location on the planet. Very dependable and memorizable thing, the clock time.
The arguments are exactly the same. It basically boils down to the philosophy if you want the daily life to be controlled by clocks or by the natural sleep/wake cycle of the body.
Some prefer by the clock, because it provides a fixed constant, even if it may run counter to our very nature. You very well may prefer that. Others argue for a more natural sleep cycle, especially when it comes to school for example. Complaints about work starting too early are not exactly rare either.