My stupid JavaScript snippets

date.js

/**
 * Date related snippets
 * @author Yu I.
 */

(function() {
    var datetime_rfc1123 = new Date(),
        datetime_iso8601 = 'YYYY-MM-DDThh:mm:ss+0000',
        unix_timestamp_1 = (datetime_rfc1123).getTime() / 1000.0,
        unix_timestamp_2 = Date(datetime_rfc1123).parse,

        convertTimestamp = function(timestamp) {
            return new Date(timestamp * 1000);
        },

        /**
         * Timeago!
         */
        getTimeago = function(timestamp) {
            var MINUTE = 60.0,
                HOUR = 3600.0,
                DAY = 86400.0,
                WEEK = 604800.0,
                MONTH = 2419200.0,
                YEAR = 29030400.0,
                current = (new Date()).getTime() / 1000.0,
                past = timestamp,
                diff = current - past,
                timeago = 'Less than a minute';

            if (0 <  Math.floor(diff / YEAR)) {
                timeago = Math.floor(diff / YEAR) + 'year(s) ago';
            }
            else if (0 <  Math.floor(diff / MONTH)) {
                timeago = Math.floor(diff / MONTH) + 'month(s) ago';
            }
            else if (0 <  Math.floor(diff / WEEK)) {
                timeago = Math.floor(diff / WEEK) + 'week(s) ago';
            }
            else if (0 <  Math.floor(diff / DAY)) {
                timeago = Math.floor(diff / DAY) + 'day(s) ago';
            }
            else if (0 <  Math.floor(diff / HOUR)) {
                timeago = Math.floor(diff / HOUR) + 'hour(s) ago';
            }
            else if (0 <  Math.floor(diff / MINUTE)) {
                timeago = Math.floor(diff / MINUTE) + 'minute(s) ago';
            }

            return timeago;
        };
})();