-1228 rc from rdefmtdate()???

We are using rdefmtdate() and rfmtdate() from a C program to convert dates from character to long integer and back. The following sample code prints rc=-1228 for each call. The error message is "Message number not found in message file." and description relates to 4GL which we are not using. Any suggestions, Thanks, jim foxj@cc.bellcore.com /*******************************************************/ main() { char cdate[11]; long idate; int rc; rc = rdefmtdate(&idate, "mmm.dd.yyyy", "01/01/1994"); printf("date 01/01/1994 rc=%d, \\n",rc); rc = rfmtdate(100,"mm/dd/yyyy",cdate); printf("date <%s> rc=%d, \\n",cdate, rc); }