Java Date Timestamp conversion issue

Question

I am doing simple String to date conversion in java, Only one thing i have to take care conversion should be in GMT. I am able to convert my String in GMT. But when i tried to convert that date into timestamp i got different value (Seems value is based on my local timezone).

    public static void timeFun(String str) throws ParseException {
    SimpleDateFormat formatter = new SimpleDateFormat("yyyy-MM-dd'T'HH:mm:ss.SSSXXX");
    String dateInString = "2015-07-10T09:54:31.000-04:00";
    Date date = formatter.parse(dateInString);

    SimpleDateFormat sdfAmerica = new SimpleDateFormat("yyyy-MM-dd'T'HH:mm:ss.SSSXXX");
    TimeZone tz = TimeZone.getTimeZone("GMT");
    sdfAmerica.setTimeZone(tz);

    String convertedDate = sdfAmerica.format(date); // Convert to String
                                                    // first
    Date dateInGMT = sdfAmerica.parse(convertedDate);
    System.out.println(convertedDate); // Output = 2015-07-10T13:54:31.000Z (Right)
    Timestamp timestamp = new java.sql.Timestamp(dateInGMT.getTime());

    System.out.println(timestamp); // Output = 2015-07-10 19:24:31.0 (Wrong)

}

The Date and Timestamp classes don't have a timezone - they only represent a number of millis since the epoch. Their toString method may do some conversions based on your machine's settings but it doesn't affect the internal state of the objects. If you use a Timestamp you probably want to interact with a DB and the result should be as you would expect (13:54GMT or some equivalent moment in time) if your database column has a time zone. — assylias
– assylias, Commented Jul 25, 2016 at 14:40

Alexander · Accepted Answer · 2016-07-25 15:02:52Z

2

Timestamp.toString() internally uses a Calendar instance with Default System Timezone. As you can see in Source Code java.util.Date.normalize() does the magic. So, yes ... The last System output is based on your local timezone.

answered Jul 25, 2016 at 15:02

Alexander

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Basil Bourque · Accepted Answer · 2016-07-25 18:09:55Z

2

The answer by Alexander is correct.

java.time

These old date-time classes are an awful mess. Avoid them, as suggested in their JavaDoc. They have been supplanted by the java.time framework.

OffsetDateTime odt = OffsetDateTime.parse( "2015-07-10T09:54:31.000-04:00" );

To get UTC (GMT), extract a Instant.

Instant instant = odt.toInstant();

To see the same moment through the lens of a particular time zone, apply a ZoneId.

ZoneId zoneId = ZoneId.of( "America/Montreal" );
ZonedDateTime zdt = instant.atZone( zoneId );

All of this has been covered many times on Stack Overflow.

answered Jul 25, 2016 at 18:09

Basil Bourque

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Andy · Accepted Answer · 2016-07-27 06:22:07Z

This code is working fine for me:

public static Timestamp convertStringToTimestamp(String strRaw) throws ParseException
  {
   SimpleDateFormat formatter = new SimpleDateFormat("yyyy-MM-dd'T'HH:mm:ss.SSSXXX");
   String dateInString = strRaw;
   Date date = formatter.parse(dateInString);
   TimeZone gmtTime = TimeZone.getTimeZone("GMT");
   formatter.setTimeZone(gmtTime);
   Calendar calendar = Calendar.getInstance(TimeZone.getTimeZone("GMT"));
   calendar.setTime(date);
   SimpleDateFormat formatter1 = new SimpleDateFormat("yyyy-MM-dd'T'HH:mm:ss.SSS");

   Timestamp t = new Timestamp(formatter1.parse(formatter.format(calendar.getTime())).getTime());

   System.out.println("********"+new Date(t.getTime()));
   return new Timestamp(formatter1.parse(formatter.format(calendar.getTime())).getTime());

  }

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