How to convert any Date time to UTC using ZonedDateTime or Java 8

I am trying to convert date 06-12-2015 02:10:10 PM from default zone to UTC using ZonedDateTime.

LocalDateTime localDateTime = LocalDateTime.ofInstant(date.toInstant(), ZoneId.systemDefault());
ZonedDateTime utc = ZonedDateTime.of(localDateTime, ZoneOffset.UTC);

but utc returns 2015-12-06T14:10:10Z instead of 06-12-2015 09:10:10 AM

How can I convert date from default zone to UTC? The answer given here convert current time to UTC.

You can use ZonedDateTime.ofInstant(Instant, ZoneId) where the second parameter is UTC (the instant knows the local offset). Something like,

String source = "06-12-2015 02:10:10 PM";
String pattern = "MM-dd-yyyy hh:mm:ss a";
DateFormat sdf = new SimpleDateFormat(pattern);
try {
    Date date = sdf.parse(source);
    ZonedDateTime zdt = ZonedDateTime.ofInstant(date.toInstant(), ZoneId.of("UTC"));
    System.out.println(zdt.format(DateTimeFormatter.ofPattern(pattern)));
} catch (ParseException e) {
    e.printStackTrace();
}

And I get (corresponding to my local zone offset)

06-12-2015 06:10:10 PM