What I am making is a weather forecast website, and what I need is the days of the week (ie. Sunday, Monday, etc.). To get tomorrow's date I am just putting + 1 like someone suggested in another question, but when it get's to Saturday, it says undefined. How do I make it so when it gets to Saturday, + 1 will loop over to Sunday? Thanks in advance!

var day=new Date();

var weekday=new Array(7);

weekday[0]=Sunday;

weekday[1]=Monday;

weekday[2]=Tuesday;

weekday[3]=Wednesday;

weekday[4]=Thursday;

weekday[5]=Friday;

weekday[6]=Saturday;



document.getElementById('tomorrow').innerHTML = weekday[day.getDay() + 1];

document.getElementById('twodays').innerHTML = weekday[day.getDay() + 2];

document.getElementById('threedays').innerHTML = weekday[day.getDay() + 3];