You want the chlorine (or other sanitizer) circulating through the system during the day when the sun is hitting the pool. Algae grows during daylight hours because it needs sun to grow.
The other advantages are:
a) it makes the pool warmer if you circulate the water during the day. b) it's usually windier at night and that's when leaves and stuff blow into the pool. You want to collect that stuff as quickly as possible because when it decomposes it generates phosphates which algae feeds on.