Different results for the same two dates in INTCK function

[Chaupak]

Hi, I met a problem when calculating the difference of months between two dates. Here are the sample codes:

data test;
	dt1 = "25Aug2011"d;
	dt2 = "23Feb2012"d;
	dt1_dt2 = intck("month",dt1,dt2,"c");
	dt2_dt1 = intck("month",dt2,dt1,"c");
	format dt1 dt2: yymmdd10.;
run;

Here I calculated the month difference between date1 2011-08-25 and date2 2012-02-23. When I put date1 before date2 (dt1_dt2) in the INTCK function, it returns 5, because the time interval is slightly <6 months. However, when I put date2 before date1 (dt2_dt1), it returns -6. Shouldn't it be -5, since I just changed the order of two dates? Anyone can help me with it?

Thanks!

[PaigeMiller · Accepted solution]

One month from 23FEB2012 is any date 23MAR2012 to 22APR 2012

Zero months from 23FEB2012 is any date 23FEB2012 to 22MAR2012.

Negative one months is any date 23JAN2012 to 22FEB2012 (so 23FEB2012 to 22FEB2012 on this scale is -1 months)

and so on

[Chaupak]

Thank you so much!

[Tom]

Another way to put it.  When you count down there is no negative zero.  The sequence is 2,1,0,-1,-2.