@DAY

@DAY[mm-dd-yy]:  Returns the numeric day of the month for the specified 
date.  DATE uses the date format and separators mandated by your country 
code (for example dd.mm.yy in Germany, or yy-mm-dd in Japan).  The year 
can be entered as a 4-digit or 2-digit value.  Two-digit years between 80 
and 99 are interpreted as 1980 - 1999; values between 00 and 79 are 
interpreted as 2000 - 2079.