Help with if..then..else statement

Shell Programming and Scripting
1

When I run the script below I get a message stating that Thu=Mon is not found. Even when I change my if statement to if $day=Thu, I get a message stating Thu=Thu is not found. How can I fix this problem?

#!/usr/bin/ksh
d=`date +%a`
if $day=Mon
then
echo Today is Monday
else
echo "$d"
fi

2 
#!/usr/bin/ksh
day=$(date +%a)
if [ "${day}" = 'Mon' ]; then
  echo Today is Monday
else
  echo "${day}"
fi