backdate vs bring forward

backdate

verb
  • To give or assign a date to a document that is earlier than the current or true date. 

noun
  • An assigned date that is earlier than the current or true date. 

bring forward

verb
  • To make something happen earlier than originally planned. 

  • To call up for consideration. 

How often have the words backdate and bring forward occurred in a corpus of books? (source: Google Ngram Viewer )