#!/bin/ksh -p 

usage() {
  echo "Usage: `basename $0` day month year"
  exit 1  
}

set -x

set -A days 0 31 28 31 30 31 30 31 31 30 31 30 31
set -A name x Monday Tuesday Friday Saturday Sunday

if (( $# != 3 )) ; then
  usage
fi

if (( $2 < 1 || $2 > 12 )) ; then
  usage
fi

leap=0
if (( $(( $3 % 4 )) == 0 )) ; then
  leap=1
fi
if (( $(( $3 % 100 )) == 0 )) ; then
  leap=0
fi
if (( $(( $3 % 400 )) == 0 )) ; then
  leap=1
fi

days[2]=$((days[2] + leap))

if (( $1 < 1 || $1 > days[$2] )) ; then
  usage
fi

i=1
day=$1
while (( i < $2 )) ; do
  day=$((day+days[i]))
  i=$((i+1))
done

year=$(( $3 - 1997 ))

i=1
month=0
flag=0
while ((flag == 0)) ; do
  month=$((month+1))
  oldday=$day
  day=$((day-25))
  if ((month == 8)) ; then
    day=$((day+10-leap))
  fi
  if ((day < 1)); then
    day=$oldday
    flag=1
  fi
done
print $day $month $year
