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.
Note that DAYS does not count the first day of the period, but NETWORKDAYS does.
DAYS is not portable to Excel.
DAYS really does return enddate - startdate; thus if either date has a time component (for example "2008-01-03T15:15"), the number of days returned may not be integer. To ensure an integer result, consider INT(DAYS()).