Calculates correct ago times for cached html pages

DateHelper.js

(function() {
    var DateHelper = {
        // Takes the format of "Jan 15, 2007 15:45:00 GMT"
        // and converts it to a relative time
        get_ago_time: function(fromDate) {
            var from = new Date();
            from.setTime(Date.parse(fromDate));
            var to = new Date();

            var distance_in_seconds = ((to - from) / 1000);
            var distance_in_minutes = Math.floor(distance_in_seconds / 60);

            if (distance_in_minutes === 0) { return 'less than a minute ago'; }
            if (distance_in_minutes == 1) { return 'a minute ago'; }
            if (distance_in_minutes < 45) { return distance_in_minutes + ' minutes ago'; }
            if (distance_in_minutes < 90) { return 'about 1 hour ago'; }
            if (distance_in_minutes < 1440) { return 'about ' + Math.floor(distance_in_minutes / 60) + ' hours ago'; }
            if (distance_in_minutes < 2880) { return '1 day ago'; }
            if (distance_in_minutes < 43200) { return Math.floor(distance_in_minutes / 1440) + ' days ago'; }
            if (distance_in_minutes < 86400) { return 'about 1 month ago'; }
            if (distance_in_minutes < 525960) { return Math.floor(distance_in_minutes / 43200) + ' months ago'; }
            if (distance_in_minutes < 1051199) { return 'about 1 year ago'; }

            return 'over ' + Math.floor(distance_in_minutes / 525960) + ' years ago';

        }
    };

    var times = document.getElementsByTagName('relative-time');
    for (i = 0; i < times.length; i++) {
        times[i].innerText = DateHelper.get_ago_time(times[i].getAttribute('datetime'));
    }

})();