There are a couple of ways I can think of to align the data.
1) format it to year month
2) use intnx function to align all date within a month to the first/last day of that month.

77   data _null_;
78       do   date='1jan2010'd to '15jan2010'd by 5;
79              date1=intnx('month',date,0,'beginning');
80              put  date / date yymmdd10. /
81                       date  yymm7. /  date1  yymmdd10. ///;
82       end;
83   run;

18263
2010-01-01
2010M01
2010-01-01



18268
2010-01-06
2010M01
2010-01-01



18273
2010-01-11
2010M01
2010-01-01

2# bobguy


太牛了