This is a more humane clock, one that fits our body's chemistry. We've evolved to speed up as the sun rises and to slow down as the sun sets. To deprive us of a correct wake up time and a correct end of work day is the same as depriving us of food and water. Set your alarms and plan your rendez-vous according to your city's sunrise and sunset times.
I wake up at D20, I'm meeting Sally for coffee at D65, and let's meet for beers at N0!