#! /usr/bin/ksh

#              ja fe ma ap ma ju ju ag se oc no de
set -A lasts 0 31 28 31 30 31 30 31 31 30 31 30 31


year=$1
month=$2
day=$3

#
# Get Day of Week of Jan 1
dow1=$(cal 1 $year | sed -n '3s/. //gp')
((dow1=7-dow1))

#
#  is this a leap year?
leap=0
if ((!(year%100))); then
     ((!(year%400))) && leap=1
else
     ((!(year%4))) && leap=1
fi

#
#  set number of days in february
lasts[2]=28
((leap)) && lasts[2]=29

#
#  calculate day of year
i=0
previous=0
while ((i < month)) ; do
     ((previous=previous+lasts[i]))
     ((i=i+1))
done
((doy=previous+day))

#
#  Calculate day of week
((dow = (doy+dow1-1)%7 ))

echo dow = $dow

exit 0

#! /usr/bin/ksh
year=$1
month=$2
day=$3

#
#  Get date of last day in 1st week of month
dldw1=$(cal $month $year | sed -n '3s/. //gp')

#
#  Calculate day of week
((dow = (day+dldw1+1)%7 ))

echo dow = $dow
exit 0