day one

Noun

 * 1) The very beginning.
 * I've been with the project since day one.
 * 1)  A close, longtime friend, one who has been around since the beginning.
 * 2) * 2017 March 17, and, "Good Life", from the soundtrack for The Fate of the Furious:
 * Raise a cup up for all my day ones; two middle fingers for the haters

Adverb

 * 1) At the very beginning; when something is entirely new.
 * to buy something day one

Translations

 * Russian: в пе́рвый же день, с пе́рвого же дня , ,