I\'m a Java developer and I\'m used to the SimpleDateFormat class that allows me to format any date to any format by settings a timezone.
Date date = new Dat
Don't write your own stuff; just get datejs: http://www.datejs.com/
You can figure out what the timezone offset is set to in the execution environment like this:
var local = new Date();
var utc = Date.UTC(local.getFullYear(), local.getMonth(), local.getDate(), local.getHours(), local.getMinutes(), local.getSeconds(), local.getMilliseconds());
var tz = (utc - local.getTime()) / (60 * 60 * 1000);