How to subtract two dates in sas studio? - sas

Question

I need help with a question.
I need to subtract two dates in sas studio. I have the next:
%let date_star = %SYSFUNC( DATETIME());
%let date_end = %SYSFUNC( DATETIME());
But I dont´n now how to subtract these variables.
Thanks for your help.

Answer 1

Use the INTCK() function to return the number of interval boundaries of a given kind that lie between two dates, times, or datetime values. The possible values of interval are listed in Date and Time Intervals.
%MACRO want;
%let date_start = %SYSFUNC(DATETIME());
data _null_;
rc=SLEEP(10,1); /* Sleep for 10 seconds */
run;
%let date_end = %SYSFUNC(DATETIME());
%put %sysfunc(intck(second, &date_start., &date_end.));
%MEND;
%want;
Result is 10 seconds, as expected.

Answer 2

So you haven't really created any variables there, just macro variables. Normally you would want to use SAS code to work with data, not macro code, but you can do it in a pinch.
You also do not have two DATE values. SAS stores dates as the number of days. Instead you have two DATETIME values. The DATETIME() function returns the number of seconds since 1960. So the difference between two datetime values will be a number in seconds.
The datetime value returned by DATETIME() will include fractions of a second. To perform floating point arithmetic in macro code you need to use the %SYSEVALF() function. The %EVAL() function that is used by default to evaluate conditions, like in a %IF statement, only handles integer arithmetic.
%let elapsed_time=%sysevalf(&date_end - &date_star);
If you would like to see the value in hours, minutes and seconds then you could apply a format to it.
%put Elasped time was %sysfunc(putn(&elapsed_time,time15.3));