sidereal day vs sunlight

sidereal day

noun
  • One day of sidereal time; the time in which Earth rotates once around its axis, relative to the point of the vernal equinox (about 23 hours, 56 minutes, 4 seconds). 

  • The rotational period of Earth; the time in which Earth rotates around its axis 360 degrees. 

sunlight

noun
  • All the electromagnetic radiation given off by the Sun, especially that in the visible spectrum that bathes the Earth. 

  • Brightness, hope; a positive outlook. 

  • Synonym of sunrise. 

verb
  • To work on the side (at a secondary job) during the daytime. 

How often have the words sidereal day and sunlight occurred in a corpus of books? (source: Google Ngram Viewer )