The format date function will output the date based on the server timezone. There is not 'automatic' conversion to UTC. However, the script to do this is simple. There are a couple of examples in the KB already (see: https://www.qvera.com/kb/index.php/127/is-there-a-way-to-change-the-time-zone-of-a-date-time-value or https://www.qvera.com/kb/index.php/1590/returning-relevent-timestamps-server-manages-multiple-zones ).
But basically, you will take your date string (wherever you got it) and run the following:
// first convert your date value from a string to a date object in java
var qieDate = qie.deduceDate(dateString);
// now we need to output the date as a formatted UTC date
var utcTimeFormat = new java.text.SimpleDateFormat('yyyy-MM-dd HH:mm:ss.SSSZ');
// now tell the new SimpleDateFormat object that you want the UTC timezone
utcTimeFormat.setTimeZone(java.util.TimeZone.getTimeZone("UTC"));
// the call to format will do the conversion and output the date in the desired format
var utcDate = utcTimeFormat.format(qieDate);
// utcDate can be placed in the message and the receiving system can process it as UTC