java - Joda DateTime to Timestamp conversion

Question

I am trying to change the value of Timestamp by DateTimeZone in Joda :

  DateTime dt = new DateTime(rs.getTimestamp("anytimestampcolumn"),
                             DateTimeZone.forID("anytimezone"));
  Timestamp ts = new Timestamp(dt.getMillis());

• For DateTime, value is : 2013-04-13T22:56:27.000+03:00

• For TimeStamp, value is : 2013-04-13 22:56:27.0

Timestamp is coming without timezone difference.

How can i get the correct Timestamp with TimeZone ? For example I want to get "2013-05-13 01:56:27.0".

Thanks in advance.

edit : using MySQL, column type is TIMESTAMP of course, rs is ResultSet.

question from:https://stackoverflow.com/questions/15994450/joda-datetime-to-timestamp-conversion

Answer 1

It is a common misconception that time (a measurable 4th dimension) is different over the world. Timestamp as a moment in time is unique. Date however is influenced how we "see" time but actually it is "time of day".

An example: two people look at the clock at the same moment. The timestamp is the same, right? But one of them is in London and sees 12:00 noon (GMT, timezone offset is 0), and the other is in Belgrade and sees 14:00 (CET, Central Europe, daylight saving now, offset is +2).

Their perception is different but the moment is the same.

You can find more details in this answer.

UPDATE

OK, it's not a duplicate of this question but it is pointless since you are confusing the terms "Timestamp = moment in time (objective)" and "Date[Time] = time of day (subjective)".

Let's look at your original question code broken down like this:

// Get the "original" value from database.
Timestamp momentFromDB = rs.getTimestamp("anytimestampcolumn");

// Turn it into a Joda DateTime with time zone.
DateTime dt = new DateTime(momentFromDB, DateTimeZone.forID("anytimezone"));

// And then turn it back into a timestamp but "with time zone".
Timestamp ts = new Timestamp(dt.getMillis());

I haven't run this code but I am certain it will print true and the same number of milliseconds each time:

System.out.println("momentFromDB == dt : " + (momentFromDB.getTime() == dt.getTimeInMillis());
System.out.println("momentFromDB == ts : " + (momentFromDB.getTime() == ts.getTime()));
System.out.println("dt == ts : " + (dt.getTimeInMillis() == ts.getTime()));

System.out.println("momentFromDB [ms] : " + momentFromDB.getTime());
System.out.println("ts [ms] : " + ts.getTime());
System.out.println("dt [ms] : " + dt.getTimeInMillis());

But as you said yourself printing them out as strings will result in "different" time because DateTime applies the time zone. That's why "time" is stored and transferred as Timestamp objects (which basically wraps a long) and displayed or entered as Date[Time].

In your own answer you are artificially adding an offset and creating a "wrong" time. If you use that timestamp to create another DateTime and print it out it will be offset twice.

// Turn it back into a Joda DateTime with time zone.
DateTime dt = new DateTime(ts, DateTimeZone.forID("anytimezone"));

P.S. If you have the time go through the very complex Joda Time source code to see how it holds the time (millis) and how it prints it.

JUnit Test as proof

import static org.junit.Assert.*;
import static org.hamcrest.CoreMatchers.*;

import java.text.SimpleDateFormat;
import java.util.Calendar;
import java.util.Date;
import java.util.Locale;
import java.util.TimeZone;

import org.junit.Before;
import org.junit.Test;


public class WorldTimeTest {
    private static final int MILLIS_IN_HOUR = 1000 * 60 * 60;
    private static final String ISO_FORMAT_NO_TZ = "yyyy-MM-dd'T'HH:mm:ss.SSS";
    private static final String ISO_FORMAT_WITH_TZ = "yyyy-MM-dd'T'HH:mm:ss.SSSXXX";

    private TimeZone londonTimeZone;
    private TimeZone newYorkTimeZone;
    private TimeZone sydneyTimeZone;
    private long nowInMillis;
    private Date now;

    public static SimpleDateFormat createDateFormat(String pattern, TimeZone timeZone) throws Exception {
        SimpleDateFormat result = new SimpleDateFormat(pattern);
        // Must explicitly set the time zone with "setCalendar()".
        result.setCalendar(Calendar.getInstance(timeZone));
        return result;
    }

    public static SimpleDateFormat createDateFormat(String pattern) throws Exception {
        return createDateFormat(pattern, TimeZone.getDefault());
    }

    public static SimpleDateFormat createDateFormat() throws Exception {
        return createDateFormat(ISO_FORMAT_WITH_TZ, TimeZone.getDefault());
    }

    public void printSystemInfo() throws Exception {
        final String[] propertyNames = {
                "java.runtime.name", "java.runtime.version", "java.vm.name", "java.vm.version",
                "os.name", "os.version", "os.arch",
                "user.language", "user.country", "user.script", "user.variant",
                "user.language.format", "user.country.format", "user.script.format",
                "user.timezone" };

        System.out.println();
        System.out.println("System Information:");
        for (String name : propertyNames) {
            if (name == null || name.length() == 0) {
                continue;
            }
            String value = System.getProperty(name);
            if (value != null && value.length() > 0) {
                System.out.println("  " + name + " = " + value);
            }
        }

        final TimeZone defaultTZ = TimeZone.getDefault();
        final int defaultOffset = defaultTZ.getOffset(nowInMillis) / MILLIS_IN_HOUR;
        final int userOffset = TimeZone.getTimeZone(System
                .getProperty("user.timezone")).getOffset(nowInMillis) / MILLIS_IN_HOUR;
        final Locale defaultLocale = Locale.getDefault();

        System.out.println("  default.timezone-offset (hours) = " + userOffset);
        System.out.println("  default.timezone = " + defaultTZ.getDisplayName());
        System.out.println("  default.timezone.id = " + defaultTZ.getID());
        System.out.println("  default.timezone-offset (hours) = " + defaultOffset);
        System.out.println("  default.locale = "
                + defaultLocale.getLanguage() + "_" + defaultLocale.getCountry()
                + " (" + defaultLocale.getDisplayLanguage()
                + "," + defaultLocale.getDisplayCountry() + ")");
        System.out.println("  now = " + nowInMillis + " [ms] or "
                + createDateFormat().format(now));
        System.out.println();
    }

    @Before
    public void setUp() throws Exception {
        // Remember this moment.
        now = new Date();
        nowInMillis = now.getTime(); // == System.currentTimeMillis();

        // Print out some system information.
        printSystemInfo();

        // "Europe/London" time zone is DST aware, we'll use fixed offset.
        londonTimeZone = TimeZone.getTimeZone("GMT");
        // The same applies to "America/New York" time zone ...
        newYorkTimeZone = TimeZone.getTimeZone("GMT-5");
        // ... and for the "Australia/Sydney" time zone.
        sydneyTimeZone = TimeZone.getTimeZone("GMT+10");
    }

    @Test
    public void testDateFormatting() throws Exception {
        int londonOffset = londonTimeZone.getOffset(nowInMillis) / MILLIS_IN_HOUR; // in hours
        Calendar londonCalendar = Calendar.getInstance(londonTimeZone);
        londonCalendar.setTime(now);

        int newYorkOffset = newYorkTimeZone.getOffset(nowInMillis) / MILLIS_IN_HOUR;
        Calendar newYorkCalendar = Calendar.getInstance(newYorkTimeZone);
        newYorkCalendar.setTime(now);

        int sydneyOffset = sydneyTimeZone.getOffset(nowInMillis) / MILLIS_IN_HOUR;
        Calendar sydneyCalendar = Calendar.getInstance(sydneyTimeZone);
        sydneyCalendar.setTime(now);

        // Check each time zone offset.
        assertThat(londonOffset, equalTo(0));
        assertThat(newYorkOffset, equalTo(-5));
        assertThat(sydneyOffset, equalTo(10));

        // Check that calendars are not equals (due to time zone difference).
        assertThat(londonCalendar, not(equalTo(newYorkCalendar)));
        assertThat(londonCalendar, not(equalTo(sydneyCalendar)));

        // Check if they all point to the same moment in time, in milliseconds.
        assertThat(londonCalendar.getTimeInMillis(), equalTo(nowInMillis));
        assertThat(newYorkCalendar.getTimeInMillis(), equalTo(nowInMillis));
        assertThat(sydneyCalendar.getTimeInMillis(), equalTo(nowInMillis));

        // Check if they all point to the same moment in time, as Date.
        assertThat(londonCalendar.getTime(), equalTo(now));
        assertThat(newYorkCalendar.getTime(), equalTo(now));
        assertThat(sydneyCalendar.getTime(), equalTo(now));

        // Check if hours are all different (skip local time because
        // this test could be executed in those exact time zones).
        assertThat(newYorkCalendar.get(Calendar.HOUR_OF_DAY),
                not(equalTo(londonCalendar.get(Calendar.HOUR_OF_DAY))));
        assertThat(sydneyCalendar.get(Calendar.HOUR_OF_DAY),
                not(equalTo(londonCalendar.get(Calendar.HOUR_OF_DAY))));


        // Display London time in multiple forms.
        SimpleDateFormat dfLondonNoTZ = createDateFormat(ISO_FORMAT_NO_TZ, londonTimeZone);
        SimpleDateFormat dfLondonWithTZ = createDateFormat(ISO_FORMAT_WITH_TZ, londonTimeZone);
        System.out.println("London (" + londonTimeZone.getDisplayName(false, TimeZone.SHORT)
                + ", " + londonOffset + "):");
        System.out.println("  time (ISO format w/o TZ) = "
                + dfLondonNoTZ.format(londonCalendar.getTime()));
        System.out.println("  time (ISO format w/ TZ)  = "
                + dfLondonWithTZ.format(londonCalendar.getTime()));
        System.out.println("  time (default format)    = "
                + londonCalendar.getTime() + " / " + londonCalendar.toString());
        // Using system default time zone.
        System.out.println("  time (default TZ)        = "
                + createDateFormat(ISO_FORMAT_NO_TZ).format(londonCalendar.getTime())
                + " / " + createDateFormat().format(londonCalendar.getTime()));


        // Display New York time in multiple forms.
        SimpleDateFormat dfNewYorkNoTZ = createDateFormat(ISO_FORMAT_NO_TZ, newYorkTimeZone);
        SimpleDateFormat dfNewYorkWithTZ = createDateFormat(ISO_FORMAT_WITH_TZ, newYorkTimeZone);
        System.out.println("New York (" + newYorkTimeZone.getDisplayName(false, TimeZone.SHORT)
                + ", " + newYorkOffset + "):");
        System.out.println("  time (ISO format w/o TZ) = "
                + dfNewYorkNoTZ.format(newYorkCalendar.getTime()));
        System.out.println("  time (ISO format w/ TZ)  = "
                + dfNewYorkWithTZ.format(newYorkCalendar.getTime()));
        System.out.println("  time (default format)    = "
                + newYorkCalendar.getTime() + " / " + newYorkCalendar.toString());
        // Using system default time zone.
        System.out.println("  time (default TZ)        = "
                + createDateFormat(ISO_FORMAT_NO_TZ).format(newYorkCalendar.getTime())
                + " / " + createDateFormat().format(newYorkCalendar.getTime()));


        // Display Sydney time in multiple forms.
        SimpleDateFormat dfSydneyNoTZ = createDateFormat(ISO_FORMAT_NO_TZ, sydneyTimeZone);
        SimpleDateFormat dfSydneyWithTZ = createDateFormat(ISO_FORMAT_WITH_TZ, sydneyTimeZone);
        System.out.println("Sydney (" + sydneyTimeZone.getDisplayName(false, TimeZone.SHORT)
                + ", " + sydneyOffset + "):");
        System.out.println("  time (ISO format w/o TZ) = "
                + dfSydneyNoTZ.format(sydneyCalendar.getTime()));
        System.out.println("  time (ISO format w/ TZ)  = "
                + dfSydneyWithTZ.format(sydneyCalendar.getTime()));
        System.out.println("  time (default format)    = "
                + sydneyCalendar.getTime() + " /