Here is an example of a SyncSort for z/OS 1.2 job that will do what you asked:
//SORT1 EXEC PGM=SORT,PARM='CENTWIN=80'
//SORTIN DD *
990126
090512
//SORTOUT DD SYSOUT=*
//SYSOUT DD SYSOUT=*
//SYSIN DD *
SORT FIELDS=COPY
OUTREC IFTHEN=(WHEN=INIT,BUILD=(1,6,Y2T)),
IFTHEN=(WHEN=INIT,BUILD=(5,2,C'/',7,2,C'/',1,4))
/*
This is the output produced: