I am working on something related. I added timezone by adding UTC to received date String.
// 2016-05-25 09:28:20 is the date received but it requires to be UTC related so that "UTC+2 ThingWorx running instance" well manage the data
var dateToParse = "2016-05-25 09:28:20";
var datePrepared = dateToParse+" UTC";
var dateFormat = "yyyy-MM-dd HH:mm:ss zzz";
var result = parseDate(datePrepared,dateFormat);
Also documentation I found useful to use the following documentation for the dateFormat: