I use it for a few things. I have it switch the Watch face on my Apple Watch at night and in the morning, so that it displays large numbers at night (I don't wear my glasses when I sleep, so big numbers are the order of the day), then switching back to my daytime watch face in the morning.
I also have one for turning the lamp in the hall on when it gets dark and off again after we go to be, and the reverse in the morning, turning it on half an hour before we usually get up and turning it off when it gets light.