agecalc.sas

%macro agecalc(date,dob) / des='Calculate age';

  /****************************************************************************
    BEGIN MACRO HEADER
   ****************************************************************************

      Name:       AgeCalc
      Author:     Chris Swenson
      Created:    2009-04-29

      Purpose:    Calculate age based on documentation found at 
                  http://support.sas.com/kb/24/808.html

      Arguments:  date - date to calculate the age from
                  dob  - date of birth of the person(s) in question

      Usage:      Use the macro as a function within a data step or procedure, 
                  for example: age=%AgeCalc(today(), DateOfBirth)

      Caution:    The formula will not work for people born on Feb 29 who 
                  celebrate on Feb 28. This code handles the celebration day as 
                  Mar 01. The code will also not work where/when the Gregorian 
                  calendar was not in use. See the online documenation for 
                  futher details.

      Notes:      The intck function returns the number of months betweeen the 
                  DOB and the date. The day functions return a 0 or 1 if the day
                  of the DOB is greater than the day of the date to correct for
                  leap years. Dividing by 12 returns the number of years, and 
                  the floor function rounds down for colloquial use.

      Revisions
      ¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯
      Date        Author  Comments
      ¯¯¯¯¯¯¯¯¯¯  ¯¯¯¯¯¯  ¯¯¯¯¯¯¯¯

      YYYY-MM-DD  III     Please use this format and insert new entries above

   ****************************************************************************
    END MACRO HEADER
   ****************************************************************************/

  floor( (intck('month', &dob, &date) - ( day(&date) < day(&dob) )) / 12)

%mend agecalc;