BASE2DATE:PROCEDURE
/* Convert base date into MM/DD/YY format */
ARG BA
BA=BA+1
DO I=1980
   OB=BA
   BA=BA-YDAYS(I)
   IF BA<=0 THEN LEAVE
END
YY=I
DM=GREG(OB,YY) /* convert offset to MM/DD/YY */
RETURN DM

/***GET YDAYS */
YDAYS:PROCEDURE
/* How many days are in a given year */
ARG YY
IF LEAP(YY) THEN RETURN 366
ELSE RETURN 365

/***GET LEAP */
LEAP:PROCEDURE
/* Return 1 if parm is leap year */
ARG YY
IF LENGTH(YY)=2 THEN DO
   IF YY>80 THEN YY='19'YY
   ELSE YY='20'YY
END
RETURN (YY%4*4=YY)

*GET GREG
GREG:PROCEDURE
/* X -> DD/MM */
ARG X,YY
IF X>366 THEN RETURN -1

DO I=1 TO 12
   OX=X
   X=X-DAYS(I,YY)
   IF X<=0 THEN LEAVE
END
MM=I
DD=OX

RETURN RIGHT(MM,2,0)'/'RIGHT(DD,2,0)'/'RIGHT(YY,2)

/***GET DAYS */
DAYS:PROCEDURE
/* We've no less days... */
/* Proc returns number of days in specific month */
ARG MM,YY
IF LENGTH(YY)=2 THEN DO
   IF YY>80 THEN YY='19'YY
   ELSE YY='20'YY
END

IF MM=2 THEN RETURN 28+LEAP(YY)
/* Dni Ada */
AD='31 28 31 30 31 30 31 31 30 31 30 31'
RETURN WORD(AD,MM)