#!/bin/csh -f

  @ yy = $1 / 10000
  @ mm = ( $1 - $yy * 10000 ) / 100
  @ dd = $1 % 100

@ dd = $dd - 1
if ( $dd == 0 ) then
    @ mm = $mm - 1
    if ( $mm == 0 ) then
        @ yy = $yy - 1
        set mm = 12
    endif
    if ( $mm == 1 ) set dd = 31
    if ( $mm == 2 ) then
        @ leap = $yy % 4
        if ( $leap == 0 ) set dd = 29
        if ( $leap != 0 ) set dd = 28
    endif
    if ( $mm == 3 ) set dd = 31
    if ( $mm == 4 ) set dd = 30
    if ( $mm == 5 ) set dd = 31
    if ( $mm == 6 ) set dd = 30
    if ( $mm == 7 ) set dd = 31
    if ( $mm == 8 ) set dd = 31
    if ( $mm == 9 ) set dd = 30
    if ( $mm == 10 ) set dd = 31
    if ( $mm == 11 ) set dd = 30
    if ( $mm == 12 ) set dd = 31
endif
if ( $yy < 10 ) set yy = 0$yy
if ( $mm < 10 ) set mm = 0$mm
if ( $dd < 10 ) set dd = 0$dd
set ymd = ${yy}${mm}${dd}
echo $ymd
