daytime vs mean solar day

daytime

noun
  • The time of daylight; the time between sunrise and sunset. 

adj
  • Happening during the day. 

  • Pertaining to daytime; appropriate to the day. 

mean solar day

noun
  • the average length of a solar day, used for practical timekeeping 

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