Date Conversion

Hi, can someone explain how to use cl to calculate dates properly?  
 
I'm using the following;
 
/* RETRIEVE THE CURRENT SYSTEM DATE & TIME */                             
             RTVSYSVAL  SYSVAL(QDATE) RTNVAR(&SYSDAT)                     
             RTVSYSVAL  SYSVAL(QTIME) RTNVAR(&SYSTIM)                     
                                                                          
/* CONVERT THE CURRENT DATE FROM MMDDYY TO YYYYMMDD */                    
             CVTDAT     DATE(&SYSDAT) TOVAR(&SYSYYMD) FROMFMT(*MDY) +     
                          TOFMT(*YYMD) TOSEP(*NONE)                       
                                                                          
/* CREATE PREVIUOS FRIDAY'S DATE BY SUBTRACTING 3 FROM CURRENT DATE */    
             CHGVAR     VAR(&PRVDAT#) VALUE(&SYSYYMD)                     
             CHGVAR     VAR(&PRVDAT#) VALUE(&PRVDAT# - 3)             
             CHGVAR     VAR(&PRVDAT) VALUE(&PRVDAT#)   
 
When I run the job on 0501 the pgm returns the date -3 as 20060498.  How would 
I have to change the code so that it returns 0429?  
 
Any examples appreciated.  
 
Thanks