By far the most powerful timer for adjusting your internal clock is light ! People who spend a lot of time outdoors and get a corresponding amount of daylight are better synchronized with the day and, on average, less nauseous. In fact, every minute of daylight brings me closer to the goal of having my internal clock match the time of day - awake in the morning, tired at night. Electric light can do this too, but much more slowly. The brighter the light, the more it can change our internal clock.
You need a bit more daylight to properly synchronize your internal clock. The more we sit in the office, the more we shift into owling, and even moderate late risers can quickly become strong owls if they don't get enough light. And that's why we're all always so tired.
