go to bed with the sun
To go to sleep at a particularly early hour, as around sundown. Mom goes to bed with the sun, so we can definitely sneak out and go to the party. The farmhands all seem to go to bed with the sun.
go to bed with the sun
Fig. to go to bed early, at sunset. The campers went to bed with the sun. The children had to go to bed with the sun. The grown-ups stayed up a little later.