Returns the number of days between two dates, using the 360 day year.
DAYS360(enddate, startdate, method)
startdate and enddate are the starting and ending dates (text or date-time serial numbers). If startdate is earlier than enddate, the result will be negative. method is an optional parameter; if 0 or omitted, the US National Association of Securities Dealers (NASD) method of calculation is used; if 1 (or <>0) the European method of calcuation is used. The calculation assumes that all months have 30 days, so a year (12 months) has 360 days.
returns 180, that is, 6 months of 30 days.