VAR [CONST] D=TIME.DATE, DAYS="SU MO TU WE TH FR SA";

FCN CENTER(TEXT,M) { STRING(" "*((M-TEXT.LEN())/2),TEXT) }

FCN ONEMONTH(YEAR,MONTH){
   DAY1:=D.ZELLER(YEAR,MONTH,1);    //1969-1-1 -->3 (WED, ISO 8601)
   DAYZ:=D.DAYSINMONTH(YEAR,MONTH); //1969-1   -->31
   LIST(CENTER(D.MONTHNAMES[MONTH],DAYS.LEN()),DAYS).EXTEND(
      (1).PUMP(DAYZ,(0).PUMP(DAY1,LIST,T(VOID,""))).APPLY("%2S ".FMT)
      .PUMP(LIST,T(VOID.READ,DAYS.LEN()/3,FALSE),STRING.CREATE));
}
...