1. Tips and Tricks Calculating age in years

2. As usual more than one way • Old school • ageinyrs=int((date of interest- birth date)/365.25); • works fine! • Newer • ageinyrs=intck(‘year’,birth date, date of interest); • works, but be careful! • Newer still • ageinyrs=floor(yrdif(birth date, date of interest, `act/act´); • works too!

3. Sample code – 1 of x *** create a test data set; data testing; informat name $3. bdaterundt future1 future2 yymmdd10.; format bdaterundt future1 future2 yymmddd10.; rundt=today(); future1='28Feb2024'd; future2='29Feb2024'd; input name bdate @@; datalines; MCB 1934-05-26 JLS 1932-12-15 PXS 1960-04-21 MXS 1962-06-06 SXS 1964-05-28 SAS 2001-10-21 RES 2005-02-01 RAN 1980-02-29 ; run;

4. Sample code – 2 of x from VIEWTABLE of data: testing

5. Sample code – 3 of x *** calculate the patient's age as of the date the program was run; data ages; set testing; *** on the run date of the program; age_m1=int((rundt-bdate)/365.25); age_m2=intck('year',bdate,rundt); age_m3=floor(yrdif(bdate,rundt,'act/act')); *** what about dates in the future?; age_m1_f1=int((future1-bdate)/365.25); age_m2_f1=intck('year',bdate,future1); age_m3_f1=floor(yrdif(bdate,future1,'act/act')); *** what about dates in the future leap years?; age_m1_f2=int((future2-bdate)/365.25); age_m2_f2=intck('year',bdate,future2); age_m3_f2=floor(yrdif(bdate,future2,'act/act')); run;

6. Printout of results: Age at run date (2013-10-17)

7. Age on 2024-02-28

8. Age on 2024-02-29

9. All methods work … but • Careful of using the intck function when calculating age • this function was developed to determine intervals for time series analysis and may round data in ways that aren’t intuitive for age calculations