astronomical day vs sunlight

astronomical day

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 astronomical day and sunlight occurred in a corpus of books? (source: Google Ngram Viewer )