I have been thinking about this for a long time now, and no one can answer it. I forget the exact length span, however, the span for each is not equal. For example, DST is 120 days, and "standard" time is 245 days. It would seem, since DST and Standard time do not cancel out (for every +1 hour, there is a -1 hour), clock time and "nature" time, would not be in sync (AM would be night, and PM would be day).
How heck does this work out in the end?
It doesn't actually have to add up in any way.
The idea is that, depending on your location on the globe, sunrise and sunset shift with the seasons.
In some places, this can cause a real problem. In the northern United States, the days get pretty short in the winter. If you don't adjust the clock, you end up with children standing on bus stops (often on very narrow roads) before the sun is up. To avoid this danger, the clock gets shifted back one hour, and now they have one more hour into the new day, to have more light when people will be out on the road.
Of course, this "steals" an hours from the end of the day, as the sun sets an hour "earlier." That's where your "cancel-out" math belongs. On an individual day, not on the system overall.
