Convert java Date time between timezones.

The standard way to specify your target timezone is GMT +/- hours minutes
e.g. for BST i can say "GMT+1"

String mytimeZone = "GMT+1";
GregorianCalendar abroad = new GregorianCalendar(TimeZone.getTimeZone(mytimeZone));
System.out.println(abroad.getTime());

//Format the timezone specific date display..
DateFormat df1 = DateFormat.getDateTimeInstance(DateFormat.FULL, DateFormat.FULL);
df1.setTimeZone(TimeZone.getTimeZone(mytimeZone));
System.out.println(df1.format(abroad.getTime()));

//Format to GMT time
df1.setTimeZone(TimeZone.getTimeZone("GMT"));
System.out.println(df1.format(abroad.getTime()));