How to set cookie expiration date to a month?

Question

i just need to set this function to expire in one month, can someone tell me how to do it?

function _saveUserPreference() {
    // Set the cookie expiry to one year after today.
    var expiryDate = new Date();
    expiryDate.setFullYear(expiryDate.getFullYear() + 1);
    document.cookie = cookieName + '=y; expires=' + expiryDate.toGMTString();
}

Answer 1

You need add one month to the expiryDate var:

  var expiryDate = new Date();
  expiryDate.setMonth(expiryDate.getMonth() + 1);