mean solar day vs night

mean solar day

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

night

noun
  • A dark blue colour, midnight blue. 

  • The period between sunset and sunrise, when a location faces far away from the sun, thus when the sky is dark. 

  • The period of darkness beginning at the end of evening astronomical twilight when the sun is 18 degrees below the horizon, and ending at the beginning of morning astronomical twilight. 

  • A night's worth of competitions, generally one game. 

  • An evening or night spent at a particular activity. 

  • A night (and part of the days before and after it) spent in a place away from home, e.g. a hotel. 

  • Darkness (due to it being nighttime). 

  • A period of time often defined in the legal system as beginning 30 minutes after sunset, and ending 30 minutes before sunrise. 

  • Nightfall. 

verb
  • To spend a night (in a place), to overnight. 

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