#!/bin/sh

month=`date +%m`
day=`date +%d`
year=`date +%Y`


month=`expr $month + 0`

day=`expr $day - 1`

if [ $day -eq 0 ]; then

  month=`expr $month - 1`

  if [ $month -eq 0 ]; then
    month=12
    day=31
    year=`expr $year - 1`

  else
    case $month in
      1|3|5|7|8|10|12) day=31;;
      4|6|9|11) day=30;;
      2)
        if [ `expr $year % 4` -eq 0 ]; then
          if [ `expr $year % 400` -eq 0 ]; then
            day=29
          elif [ `expr $year % 100` -eq 0 ]; then
            day=28
          else
            day=29
          fi
        else
          day=28
        fi
      ;;
    esac
  fi
fi

ydate="$year-$month-$day"
echo $ydate

exit 0

pWd=/path/to/my/logs
prefix=my.log.
if [ -e $prefix$date ]
    then
        gzip $prefix$date;
fi