PARM D0_DATE

# DAYS.XEQ - RETURNS NUMBER OF DAYS SINCE DEC 31, 1899
# D0_DATE MUST BE A DATE ON OR AFTER 1900/01/01 IN YYYYMMDD FORM.
# TIM ERICSON  07/14/1998
# FIX LEAP YEAR ERROR 09/16/1998

# EXTRACT THE YEAR, MONTH, AND DAY FROM THE INPUT DATE
SETVAR D0_YEAR,  STR ( "!D0_DATE", 1, 4 )
SETVAR D0_MONTH, STR ( "!D0_DATE", 5, 2 )
SETVAR D0_DAYS,  STR ( "!D0_DATE", 7, 2 )

# MAKE SURE THE YEAR, MONTH, AND DAY ARE NUMERIC
SETVAR D0_YEAR,  !D0_YEAR
SETVAR D0_MONTH, !D0_MONTH
SETVAR D0_DAYS,  !D0_DAYS

# DO *SOME* ERROR CHECKING
IF D0_YEAR  < 1900 &
OR D0_MONTH > 12   &
OR D0_MONTH < 1    &
OR D0_DAYS  > 31   &
OR D0_DAYS  < 1
  ECHO
  ECHO ERROR! !D0_DATE is an invalid date!
  ECHO
  RETURN
ENDIF

# CALCULATE THE TOTAL DAYS BEFORE THE CURRENT YEAR
# IF IT'S *AFTER* FEBRUARY, OR THIS IS *NOT* A LEAP YEAR -
# NO ADJUSTMENT.  IF THIS *IS* A LEAP YEAR, ADJUST.
# REMEMBER - THE CI DOES INTEGER MATH! (FRACTIONS ARE
# DROPPED!)
IF D0_MONTH > 2 &
OR D0_YEAR MOD 4 <> 0 &
OR ( D0_YEAR MOD 100 = 0 AND D0_YEAR MOD 400 <> 0 )
  SETVAR D0_YEAR_DAYS, ( ( !D0_YEAR - 1900 ) * 1461 ) / 4
ELSE
  SETVAR D0_YEAR_DAYS, ( ( ( !D0_YEAR - 1900 ) * 1461 ) / 4 ) - 1
ENDIF

# CALCULATE THE TOTAL DAYS BEFORE THE CURRENT MONTH
SETVAR D0_MONTH_DAYS, 0
WHILE D0_MONTH > 1 DO
  SETVAR D0_MONTH, D0_MONTH - 1
  SETVAR D0_MONTH_DAYS, D0_MONTH_DAYS + &
    ![ STR ( "312831303130313130313031", ( 2 * D0_MONTH ) - 1, 2 ) ]
ENDWHILE

# ADD IT ALL UP INTO THE RETURN VARIABLE
SETVAR RETURN_DAYS, D0_YEAR_DAYS + D0_MONTH_DAYS + D0_DAYS

DELETEVAR D0_@