Convert Days into Year

#!/bin/bash
# Source : DaysToYear.sh
# Convert days into year

echo -n "Enter current year : "
read year

echo -n "Enter Days : "
read day
dd=$day
yy=-1

while [ $day -gt 0 ]
do
if [ `expr $year % 4` -eq 0 ]
then
d=`expr $day % 366`
day=`expr $day - 366`
echo "$year is Leap year."
else
d=`expr $day % 365`
day=`expr $day - 365`
fi
year=`expr $year + 1`
yy=`expr $yy + 1`
done
echo "$dd days = $yy years & $d days."