Understanding dates

CSS

.important {
    font-weight: bold;
    color: red;
}

JavaScript

var dates=['2012-07-01', '2012-07-09', '2012-07-10', '2012-07-31', '2012-08-1', '2012-08-9', '2012-08-10', '2012-08-31', '2012-09-1', '2012-09-9', '2012-09-10', '2012-12-09', '2012-12-31', '2013-01-01', '2013-01-09', '2013-02-09', '2013-03-09', '2013-04-09', '2013-05-09', '2013-06-09', '2013-07-09', '2013-08-09', '2013-09-09']

var regex = /^(.* == [a-zA-Z]{3} )([a-zA-Z]{3} [0-9]+)(.*)$/
function emphasize(str){
    return str.replace(regex, "$1<span class='important'>$2</span>$3")
}
    
dates.forEach(function (datestr){
    var date = new Date(datestr);
    $('body').append(emphasize("new Date('"+datestr+"') == " + date + '<br/>'));
});