Well, from what I have read in magazine articles, or heard some hunting pro on TV talk about... I think it has to do with the sun/moon phases or maybe weather patterns.

When the sunset and moonrise are almost at the same time (Full Moon), the deer are supposed to be incredibly active. It's why a lot of websites, articles, hunting/fishing charts all say "Excellent".

When the sunrise and moonrise are almost at the same time, (New Moon), the deer are again supposed to be incredibly active. It's why a lot of websites, articles, hunting/fishing charts all say "Excellent" again.