See a??$ZDate()a?? for the usage of $ZDATEFORM. $ZDATEFORM also defines the behavior of some date and time utility routines; refer "M utility Routines".
Example:
GTM>WRITE $ZDATEFROM 0 GTM>WRITE $ZDATE($H) 11/15/02 GTM>SET $ZDATEFORM=1 GTM>WRITE $ZDATE($H) 11/15/2002