格式化XmlGregorianCalendar时区问题(Formatting XmlGregorianCalendar timezone issue)

I need to format java XmlGregorianCalendar to "yyMMdd" string.
　　My implementation:
　　XMLGregorianCalendar date=getDate(); //getting the date
　　if (date !=null) {
　　SimpleDateFormat sdf=new SimpleDateFormat("yyMMdd");
　　LOG.debug("Parsing date...");
　　LOG.debug("XML Date: " + date);
　　LOG.debug("XML Date timezone: " + date.getTimezone());
　　GregorianCalendar gc=date.toGregorianCalendar();
　　LOG.debug("Gregorian calendar: " + gc.toString());
　　LOG.debug("Gregorian calendar timezone id: " + gc.getTimeZone().getID());
　　Date d=gc.getTime();
　　LOG.debug("Date: " + d.toString());
　　String formatted=sdf.format(d);
　　LOG.debug("Formatted: " + formatted);
　　}

　　What I see in log:

　　Parsing date...

　　XML Date: 1943-04-15T00:00:00.000Z

　　XML Date timezone: 0

　　Gregorian calendar: java.util.GregorianCalendar[time=?,areFieldsSet=false,areAllFieldsSet=true,lenient=true,zone=sun.util.calendar.ZoneInfo[id="GMT+00:00",offset=0,dstSavings=0,useDaylight=false,transitions=0,lastRule=null],firstDayOfWeek=1,minimalDaysInFirstWeek=1,ERA=1,YEAR=1943,MONTH=3,WEEK_OF_YEAR=1,WEEK_OF_MONTH=1,DAY_OF_MONTH=15,DAY_OF_YEAR=1,DAY_OF_WEEK=5,DAY_OF_WEEK_IN_MONTH=1,AM_PM=0,HOUR=0,HOUR_OF_DAY=0,MINUTE=0,SECOND=0,MILLISECOND=0,ZONE_OFFSET=0,DST_OFFSET=0]

　　Gregorian calendar timezone id: GMT+00:00

　　Date: Wed Apr 14 20:00:00 EDT 1943

　　Formatted: 430414

　　April, 15 was parsed as April, 14. What I'm doing wrong? When I should set timezone?

　　盾畳圭宛

　　It was parsed as midnight on April 15th UTC. It was then formatted as 8pm on April 14th EDT, which is correct as EDT is four hours behind UTC.

　　Note that Date.toString() always uses the local time zone - a Date object has no concept of which time zone it's in.

　　Your formatted value is also using the default time zone, as you haven't specified a time zone. The calendar value (gc) is in UTC, but when you format it, it will apply the time zone from the formatter (as you format the Date value, which doesn't have a time zone).

　　It's not clear what you were trying to achieve, but hopefully that will help. As an aside, I'd strongly recommend that you use Joda Time instead if you possibly can - it makes a lot of this much clearer.