Returns the number of days between two dates
startdate and enddate may be dates as numbers or text (which is converted to number form). DAYS returns enddate - startdate. The result may be negative.
returns 2, the number of days between 1March08 and 3March08.
where cell A1 contains the date 2008-06-09 and A2 contains 2008-06-02 returns 7.