forever after vs one day

forever after

adv

  • forever, from this point onward 

one day

adv

  • At some unspecified time in the future. 

  • Used other than figuratively or idiomatically: see one, day. 

  • At some unspecified time in the past. 

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