JS help

Question

Need help with JS... Not sure what I'm doing wrong
Sundays in Switzerland are protected with Quiet Rules which make it illegal to pursue certain activities.
Taking the day of the week as input, output to the console "Obey the rules" if it is Sunday.

function main() {
var day = readLine();
var rules = 'Obey the rules';
// Your code goes here
if (day='sunday') console.log(rules);
}
Any day it enters it displays the 'rules'.