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 time zone is not specified in the String from which Date is parsed  I want to set a specific time zone of the date object   How can I do that

User · Answer

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;
}

Credit goes to this post.

User · Answer

Here you be able to get date like  quot 2020-03-11T20 16 17 quot  and return  quot 11 Mar 2020 - 20 16 quot   private String transformLocalDateTimeBrazillianUTC String dateJson  throws  ParseException       String localDateTimeFormat    quot yyyy-MM-dd T HH mm ss quot       SimpleDateFormat formatInput   new SimpleDateFormat localDateTimeFormat          Here is will set the time zone     formatInput setTimeZone TimeZone getTimeZone  quot UTC-03 quot          String brazilianFormat    quot dd MMM yyyy - HH mm quot       SimpleDateFormat formatOutput   new SimpleDateFormat brazilianFormat       Date date   formatInput parse dateJson       return formatOutput format date

User · Answer

java util Calendar is the usual way to handle time zones using just JDK classes  Apache Commons has some further alternatives utilities that may be helpful  Edit Spong s note reminded me that I ve heard really good things about Joda-Time  though I haven t used it myself

User · Answer

If anyone ever needs this  if you need to convert an XMLGregorianCalendar timezone to your current timezone from UTC  then all you need to do is set the timezone to 0  then call toGregorianCalendar   - it will stay the same timezone  but the Date knows how to convert it to yours  so you can get the data from there    XMLGregorianCalendar xmlStartTime   DatatypeFactory newInstance        newXMLGregorianCalendar            GregorianCalendar GregorianCalendar getInstance     xmlStartTime setTimezone 0   GregorianCalendar startCalendar   xmlStartTime toGregorianCalendar    Date startDate   startCalendar getTime    XMLGregorianCalendar xmlStartTime   DatatypeFactory newInstance        newXMLGregorianCalendar startCalendar   xmlStartTime setHour startDate getHours     xmlStartTime setDay startDate getDate     xmlStartTime setMinute startDate getMinutes     xmlStartTime setMonth startDate getMonth   1   xmlStartTime setTimezone -startDate getTimezoneOffset     xmlStartTime setSecond startDate getSeconds     xmlStartTime setYear startDate getYear     1900   System out println xmlStartTime toString       Result   2015-08-26T12 02 27 183Z 2015-08-26T14 02 27 183 02 00

User · Answer

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

User · Answer

Convert the Date to String and do it with SimpleDateFormat       SimpleDateFormat readFormat   new SimpleDateFormat  yyyy-MM-dd T HH mm ss        readFormat setTimeZone TimeZone getTimeZone  GMT    timezoneOffset        String dateStr   readFormat format date       SimpleDateFormat writeFormat   new SimpleDateFormat  yyyy-MM-dd T HH mm ss        Date date   writeFormat parse dateStr

User · Answer

tl dr     parsed     from a String     time zone is not specified     I want to set a specific time zone  LocalDateTime parse   quot 2018-01-23T01 23 45 123456789 quot        Parse string  lacking an offset-from-UTC and lacking a time zone  as a  LocalDateTime        atZone  ZoneId of   quot Africa Tunis quot                      Assign the time zone for which you are certain this date-time was intended  Instantiates a  ZonedDateTime  object   No Time Zone in j u Date As the other correct answers stated  a java util Date has no time zone     It represents UTC GMT  no time zone offset   Very confusing because its toString method applies the JVM s default time zone when generating a String representation  Avoid j u Date For this and many other reasons  you should avoid using the built-in java util Date  amp   Calendar  amp  java text SimpleDateFormat  They are notoriously troublesome  Instead use the java time package bundled with Java 8  java time The java time classes can represent a moment on the timeline in three ways   UTC  Instant  With an offset  OffsetDateTime with ZoneOffset  With a time zone  ZonedDateTime with ZoneId   Instant In java time  the basic building block is Instant  a moment on the time line in UTC  Use Instant objects for much of your business logic  Instant instant   Instant now     OffsetDateTime Apply an offset-from-UTC to adjust into some locality   s wall-clock time  Apply a ZoneOffset to get an OffsetDateTime  ZoneOffset zoneOffset   ZoneOffset of   quot -04 00 quot     OffsetDateTime odt   OffsetDateTime ofInstant  instant   zoneOffset     ZonedDateTime Better is to apply a time zone  an offset plus the rules for handling anomalies such as Daylight Saving Time  DST   Apply a ZoneId to an Instant to get a ZonedDateTime  Always specify a proper time zone name  Never use 3-4 abbreviations such as EST or IST that are neither unique nor standardized  ZoneId zoneId   ZoneId of   quot America Montreal quot     ZonedDateTime zdt   ZonedDateTime ofInstant  instant   zoneId     LocalDateTime If the input string lacked any indicator of offset or zone  parse as a LocalDateTime  If you are certain of the intended time zone  assign a ZoneId to produce a ZonedDateTime  See code example above in tl dr section at top  Formatted Strings Call the toString method on any of these three classes to generate a String representing the date-time value in standard ISO 8601 format  The ZonedDateTime class extends standard format by appending the name of the time zone in brackets  String outputInstant   instant toString       Ex  2011-12-03T10 15 30Z String outputOdt   odt toString       Ex  2007-12-03T10 15 30 01 00 String outputZdt   zdt toString       Ex  2007-12-03T10 15 30 01 00 Europe Paris   For other formats use the DateTimeFormatter class  Generally best to let that class generate localized formats using the user   s expected human language and cultural norms  Or you can specify a particular format     About java time The java time framework is built into Java 8 and later  These classes supplant the troublesome old legacy date-time classes such as java util Date  Calendar   amp  SimpleDateFormat  To learn more  see the Oracle Tutorial  And search Stack Overflow for many examples and explanations  Specification is JSR 310  The Joda-Time project  now in maintenance mode  advises migration to the java time classes  You may exchange java time objects directly with your database  Use a JDBC driver compliant with JDBC 4 2 or later  No need for strings  no need for java sql   classes  Hibernate 5  amp  JPA 2 2 support java time  Where to obtain the java time classes   Java SE 8  Java SE 9  Java SE 10  Java SE 11  and later  - Part of the standard Java API with a bundled implementation   Java 9 brought some minor features and fixes    Java SE 6 and Java SE 7  Most of the java time functionality is back-ported to Java 6  amp  7 in ThreeTen-Backport    Android  Later versions of Android  26   bundle implementations of the java time classes  For earlier Android   lt 26   a process known as API desugaring brings a subset of the java time functionality not originally built into Android   If the desugaring does not offer what you need  the ThreeTenABP project adapts ThreeTen-Backport  mentioned above  to Android  See How to use ThreeTenABP           Joda-Time While Joda-Time is still actively maintained  its makers have told us to migrate to java time as soon as is convenient  I leave this section intact as a reference  but I suggest using the java time section above instead  In Joda-Time  a date-time object  DateTime  truly does know its assigned time zone  That means an offset from UTC and the rules and history of that time zone   s Daylight Saving Time  DST  and other such anomalies  String input    quot 2014-01-02T03 04 05 quot   DateTimeZone timeZone   DateTimeZone forID   quot Asia Kolkata quot     DateTime dateTimeIndia   new DateTime  input  timeZone    DateTime dateTimeUtcGmt   dateTimeIndia withZone  DateTimeZone UTC     Call the toString method to generate a String in ISO 8601 format  String output   dateTimeIndia toString     Joda-Time also offers rich capabilities for generating all kinds of other String formats  If required  you can convert from Joda-Time DateTime to a java util Date  Java util Date date   dateTimeIndia toDate     Search StackOverflow for  quot joda date quot  to find many more examples  some quite detailed      Actually there is a time zone embedded in a java util Date  used for some internal functions  see comments on this Answer   But this internal time zone is not exposed as a property  and cannot be set  This internal time zone is not the one used by the toString method in generating a string representation of the date-time value  instead the JVM   s current default time zone is applied on-the-fly  So  as shorthand  we often say    j u Date has no time zone     Confusing  Yes  Yet another reason to avoid these tired old classes

User · Answer

Use DateFormat  For example   SimpleDateFormat isoFormat   new SimpleDateFormat  yyyy-MM-dd T HH mm ss    isoFormat setTimeZone TimeZone getTimeZone  UTC     Date date   isoFormat parse  2010-05-23T09 01 02

User · Answer

This code was helpful in an app I m working on       Instant date   null      Date sdf   null      String formatTemplate    EEE MMM dd yyyy HH mm ss       try           SimpleDateFormat isoFormat   new SimpleDateFormat  EEE MMM dd yyyy HH mm ss            isoFormat setTimeZone TimeZone getTimeZone ZoneId of  US Pacific              sdf   isoFormat parse timeAtWhichToMakeAvailable           date   sdf toInstant           catch  Exception e            System out println  did not parse      timeAtWhichToMakeAvailable              LOGGER info  timeAtWhichToMakeAvailable      timeAtWhichToMakeAvailable       LOGGER info  sdf      sdf       LOGGER info  parsed to      date

User · Answer

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

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

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