day one vs to start with

day one

adv

  • At the very beginning; when something is entirely new. 

noun

  • A close, longtime friend, one who has been around since the beginning. 

  • The very beginning. 

to start with

adv

  • Synonym of to begin with 

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