#!/bin/bash

printf -v day '%(%a)T'

case $day in 
    Sat|Sun) echo "Hooray!";;
    *) echo "Go back to work! It's $day";;
esac

case $(printf -v day '%(%a)T') in 
    Sat|Sun) echo "Hooray!";;
    *) echo "Go back to work! It's $day";;
esac