Why am I more energized during night time then day time when the sun is out?

Whenever it is sunny and hot outside I seem to loose my energy quickly, but at night i get it all back. Even when I am tired from soccer the day before (tired as in hard to run for more than a few seconds without running out of breath, and aching leg muscles) it seems to heal up and re energize during the night when the sun is down. Why?