Practitioners of demonic cultivation change with the seasons.

To put it simply, they primarily cultivate the power of yin. Therefore, the closer it gets to nighttime, the more active they become. Being nocturnal is their nature.

However, this doesn't mean they must only come out at night.

Just like righteous cultivators, whose primary activities occur during the day, and who enter meditation at night to harmonize the yin of the night with the yang within them.