Excel Date formatting

Looks like a rookie problem, but I've tried everything I know...

Cannot re-format date from 1900 number to usable format.  Would like to have Month-Day.  Had it displaying like I wanted, and then it just changed to 43415 instead of 11/11/2018.  Changing cell format results in same display.  Other cells are dependent on this value (i.e. =A2+7 for date a week later).  

Cells were set to format as mmm d, but still displays =A2+7