Voila un script qui doit fonctionner :

#!/bin/ksh
#
set -A DAYS Sat Sun Mon Tue Wed Thu Fri Sat
set -A MONTHS Dec Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
#
# fonctionne sous Linux
#
# date -d '1 days ago'
#
YESTERDAY=$((`date +%d` -1))
MONTH=`date +%m`
YEAR=`date +%Y`
NDAY=`date +%u`
WEEKDAY=${DAYS[`date +%u`]}
#
if [ $YESTERDAY -eq "0" ];
then
#
MONTH=$((MONTH-1))
#
if [ $MONTH -eq "0" ];
then
#
MONTH=12
YEAR=$((YEAR-1))
#
fi
#
set `cal $MONTH ${YEAR}`
shift $(($# - 1))
YESTERDAY=$1
#
fi
#
TMONTH=${MONTHS[MONTH]}
YEAR2=${YEAR##20}
#
# uncomment next line for debugging
#
echo ${WEEKDAY} ${YESTERDAY} ${TMONTH} ${YEAR}
#
echo ${YESTERDAY}${MONTH}${YEAR2}
#