Since the beginning of my SAS experience way back in 1996, I've been disappointed with the MDY(month,day,year) function. As you know, MDY() has the following constraints: month - specifies a numeric constant, variable, or expression that represents an integer from 1 through 12. day - specifies a numeric constant, variable, or expression that represents an integer from 1 through 31. MDY() will return an error if those constraints are not met. Let me tell you why I'm disappointed. I used Excel for several years prior to learning SAS and grew accustomed to its DATE(year,month,day) function. As you may know, the DATE() function behaves just like MDY(), but without the constraints. Here is where it gets interesting. Suppose you wanted to determine the last day of a particular month, say March. With the date() function, you can simply enter the first day of the following month minus one day, e.g., =date(2011,1,3+1)-1 In this case, I compute the first day of April and subtract one day to get the last day of march. Of course, this logic will work with MDY as well: mdy(3+1,1,2011) - 1 However, MDY() will error out if I'm at month 12, e.g. mdy(12+1,1,2011) -1 This is not the case with Excel's date function as it can handle any month integer. Month 13 is simply the following year's month 1, e.g. 1/1/2012 = date(2011,13,1) There are many useful cases there you might want to cycle through months or days outside of MDY()'s constraints. So I created my own function called ymd(year,month,day) which removes these constraints. Here it is if you want to try it: proc fcmp outlib=work.subs.ymd; function ymd(year,month,day) ; year_add = floor((month-1)/12); monthnum = ((month - 1) - 12*year_add)+1; d = mdy(monthnum,1,year+year_add) + (day - 1); return(d); endsub; run; quit; Dave
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