get relative time in js

time.js

function relative_time(date_str) {
    if (!date_str) {return;}
    var parsed_date = date_str;
    var relative_to = (arguments.length > 1) ? arguments[1] : new Date(); //defines relative to what ..default is now
    var delta = parseInt((relative_to.getTime()-parsed_date)/1000);
    delta=(delta<2)?2:delta;
    var r = '';
    if (delta < 60) {
    r = delta + ' seconds ago';
    } else if(delta < 120) {
    r = 'a minute ago';
    } else if(delta < (45*60)) {
    r = (parseInt(delta / 60, 10)).toString() + ' minutes ago';
    } else if(delta < (2*60*60)) {
    r = 'an hour ago';
    } else if(delta < (24*60*60)) {
    r = '' + (parseInt(delta / 3600, 10)).toString() + ' hours ago';
    } else if(delta < (48*60*60)) {
    r = 'a day ago';
    } else {
    r = (parseInt(delta / 86400, 10)).toString() + ' days ago';
    }
    return 'about ' + r;
};