In "The Great Gatsby," how long has it been since Gatsby and Daisy have been together?

Jordan recalls for Nick how Daisy and Jay met in chapter 4.  The year was 1917.  Though the reader doesn't know yet that the current year of the story is 1922.  Next this five year span of time is mentioned specifically again in chapter 5.  Nick has invited Daisy to his house for tea, at Jay's request.  Daisy and Jay see each other and Daisy comments that they haven't seen each other "...for many years."  Jay says, "Five years next November."  Jay has carefully noted the time which tells the reader how important that passage of time was.  Later, in chapter 6, Jay recalls to Nice about the first kiss that passed between the two of them, "...One autumn night, five years before, ...".

Coincidentally, it was five years that Jay Gatsby spent with Dan Cody transforming from James Gatz into Jay Gatsby.