by and by vs mañana

by and by

adv

  • After a short time. 

  • After an indefinite period. 

noun

  • Heaven; the hereafter. Usually preceded with "the sweet." 

mañana

adv

  • Some unspecified time in the future. 

  • Tomorrow. 

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