sidereal day vs week

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. 

week

noun
  • Any period of seven consecutive days. 

  • A period of five days beginning with Monday. 

  • A subdivision of the month into longer periods of work days punctuated by shorter weekend periods of days for markets, rest, or religious observation such as a sabbath. 

  • A period of seven days beginning with Sunday or Monday. 

adj
  • Seven days after (sometimes before) a specified date. 

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