On normal days, probably the mornings. Like Sensenmann, I'm not a morning person and would prefer to wake up later in the day.
On bad days (like today), it's the whole 24 hours.
As cliche as it is, stepping out into the sun does make me feel better. The dose of vitamin D does reduce my depressive symptoms.
Problem is, I really enjoy my introversion and staying in my room more than the outside.