How to set time zone of a java.util.Date?

Question

I have parsed a java.util.Date from a String but it is setting the local time zone as the time zone of the date object.

The ti

Answer 1

You could also set the timezone at the JVM level

Date date1 = new Date();
System.out.println(date1);

TimeZone.setDefault(TimeZone.getTimeZone("UTC"));
// or pass in a command line arg: -Duser.timezone="UTC"

Date date2 = new Date();
System.out.println(date2);

output:

Thu Sep 05 10:11:12 EDT 2013
Thu Sep 05 14:11:12 UTC 2013

Answer 2

Here you be able to get date like "2020-03-11T20:16:17" and return "11/Mar/2020 - 20:16"

 private String transformLocalDateTimeBrazillianUTC(String dateJson) throws  ParseException {
    String localDateTimeFormat = "yyyy-MM-dd'T'HH:mm:ss";
    SimpleDateFormat formatInput = new SimpleDateFormat(localDateTimeFormat);

    //Here is will set the time zone
    formatInput.setTimeZone(TimeZone.getTimeZone("UTC-03"));

    String brazilianFormat = "dd/MMM/yyyy - HH:mm";
    SimpleDateFormat formatOutput = new SimpleDateFormat(brazilianFormat);
    Date date = formatInput.parse(dateJson);
    return formatOutput.format(date);
}

Answer 3

Be aware that java.util.Date objects do not contain any timezone information by themselves - you cannot set the timezone on a Date object. The only thing that a Date object contains is a number of milliseconds since the "epoch" - 1 January 1970, 00:00:00 UTC.

As ZZ Coder shows, you set the timezone on the DateFormat object, to tell it in which timezone you want to display the date and time.

Answer 4

If you must work with only standard JDK classes you can use this:

/**
 * Converts the given <code>date</code> from the <code>fromTimeZone</code> to the
 * <code>toTimeZone</code>.  Since java.util.Date has does not really store time zome
 * information, this actually converts the date to the date that it would be in the
 * other time zone.
 * @param date
 * @param fromTimeZone
 * @param toTimeZone
 * @return
 */
public static Date convertTimeZone(Date date, TimeZone fromTimeZone, TimeZone toTimeZone)
{
    long fromTimeZoneOffset = getTimeZoneUTCAndDSTOffset(date, fromTimeZone);
    long toTimeZoneOffset = getTimeZoneUTCAndDSTOffset(date, toTimeZone);

    return new Date(date.getTime() + (toTimeZoneOffset - fromTimeZoneOffset));
}

/**
 * Calculates the offset of the <code>timeZone</code> from UTC, factoring in any
 * additional offset due to the time zone being in daylight savings time as of
 * the given <code>date</code>.
 * @param date
 * @param timeZone
 * @return
 */
private static long getTimeZoneUTCAndDSTOffset(Date date, TimeZone timeZone)
{
    long timeZoneDSTOffset = 0;
    if(timeZone.inDaylightTime(date))
    {
        timeZoneDSTOffset = timeZone.getDSTSavings();
    }

    return timeZone.getRawOffset() + timeZoneDSTOffset;
}

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