Convert Date Time for given Timezone - java

Question

I want to convert this GMT time stamp to GMT 13   2011-10-06 03 35 05   I have tried about 100 different combinations of DateFormat  TimeZone  Date  GregorianCalendar etc  to try to do this VERY basic task   This code does what I want for the CURRENT TIME   Calendar calendar   new GregorianCalendar TimeZone getTimeZone  GMT      DateFormat formatter   new SimpleDateFormat  dd MMM yyyy HH mm ss z        formatter setTimeZone TimeZone getTimeZone  GMT 13        String newZealandTime   formatter format calendar getTime       But what I want is to set the time rather than using the current time    I found that anytime I try to set the time like this   calendar setTime new Date 1317816735000L      the local machine s TimeZone is used  Why is that  I know that when  new Date    returns UTC 0 time so why when you set the Time in milliseconds does it no longer assume the time is in UTC   Is it possible to    Set the time on an object  Calendar Date TimeStamp   Possibly  Set the TimeZone of the initial time stamp  calendar setTimeZone       Format the time stamp with a new TimeZone  formatter setTimeZone        Return a string with new time zone time   formatter format calendar getTime       Thanks in advance for any help  D

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Joda-Time  The java util Date Calendar classes are a mess and should be avoided   Update  The Joda-Time project is in maintenance mode  The team advises migration to the java time classes   Here s your answer using the Joda-Time 2 3 library  Very easy   As noted in the example code  I suggest you use named time zones wherever possible so that your programming can handle Daylight Saving Time  DST  and other anomalies   If you had placed a T in the middle of your string instead of a space  you could skip the first two lines of code  dealing with a formatter to parse the string  The DateTime constructor can take a string in ISO 8601 format         2013 Basil Bourque  This source code may be used freely forever by anyone taking full responsibility for doing so     import org joda time       import org joda time format        Parse string as a date-time in UTC  no time zone offset   DateTimeFormatter formatter   org joda time format DateTimeFormat forPattern   yyyy-MM-dd   HH mm ss     DateTime dateTimeInUTC   formatter withZoneUTC   parseDateTime   2011-10-06 03 35 05         Adjust for 13 hour offset from UTC GMT  DateTimeZone offsetThirteen   DateTimeZone forOffsetHours  13    DateTime thirteenDateTime   dateTimeInUTC toDateTime  offsetThirteen        Hard-coded offsets should be avoided  Better to use a desired time zone for handling Daylight Saving Time  DST  and other anomalies     Time Zone list    http   joda-time sourceforge net timezones html DateTimeZone timeZoneTongatapu   DateTimeZone forID   Pacific Tongatapu     DateTime tongatapuDateTime   dateTimeInUTC toDateTime  timeZoneTongatapu      Dump those values     System out println   dateTimeInUTC      dateTimeInUTC    System out println   thirteenDateTime      thirteenDateTime    System out println   tongatapuDateTime      tongatapuDateTime      When run     dateTimeInUTC  2011-10-06T03 35 05 000Z thirteenDateTime  2011-10-06T16 35 05 000 13 00 tongatapuDateTime  2011-10-06T16 35 05 000 13 00

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As always  I recommend reading this article about date and time in Java so that you understand it   The basic idea is that  under the hood  everything is done in UTC milliseconds since the epoch  This means it is easiest if you operate without using time zones at all  with the exception of String formatting for the user   Therefore I would skip most of the steps you have suggested    Set the time on an object  Date  Calendar etc   Set the time zone on a formatter object  Return a String from the formatter    Alternatively  you can use Joda time  I have heard it is a much more intuitive datetime API

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For me  the simplest way to do that is   Calendar calendar   Calendar getInstance    calendar setTime new Date     SimpleDateFormat sdf   new SimpleDateFormat  yyyy-MM-dd hh mm ss       Here you say to java the initial timezone  This is the secret sdf setTimeZone TimeZone getTimeZone  UTC       Will print in UTC System out println sdf format calendar getTime             Here you set to your timezone sdf setTimeZone TimeZone getDefault       Will print on your default Timezone System out println sdf format calendar getTime

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Your approach works without any modification   Calendar calendar   Calendar getInstance TimeZone getTimeZone  GMT        Timestamp for 2011-10-06 03 35 05 GMT calendar setTime new Date 1317872105000L     DateFormat formatter   new SimpleDateFormat  yyyy-MM-dd HH mm ss z     formatter setTimeZone TimeZone getTimeZone  GMT 13         Prints 2011-10-06 16 35 05 GMT 13 00 System out println formatter format calendar getTime

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public Timestamp convertLocalTimeToServerDatetime String dt String timezone        String clientDnT   dt      2017-06-01 07 20 00       try      SimpleDateFormat sdf   new SimpleDateFormat  yyyy-MM-dd HH mm ss        Date date   sdf parse clientDnT       TimeZone tz   TimeZone getTimeZone timezone trim        get time zone of user     sdf setTimeZone tz           Convert to servertime zone      SimpleDateFormat sdf1   new SimpleDateFormat  yyyy-MM-dd HH mm ss        TimeZone tzInAmerica   TimeZone getDefault        sdf1 setTimeZone tzInAmerica           assign date to date     String serverDate   sdf1 format date           Convert to servertime zone to Timestamp     Date date2    sdf parse serverDate       Timestamp tsm   new Timestamp date2 getTime         return  tsm            catch Exception e           System err println e              return null

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We can get the UTC GMT time stamp from the given date          Get the time stamp in GMT UTC by passing the valid time  dd-MM-yyyy HH mm ss      public static long getGMTTimeStampFromDate String datetime        long timeStamp   0      Date localTime   new Date         String format    dd-MM-yyyy HH mm ss       SimpleDateFormat sdfLocalFormat   new SimpleDateFormat format       sdfLocalFormat setTimeZone TimeZone getDefault          try            localTime    Date  sdfLocalFormat parse datetime             Calendar cal   Calendar getInstance TimeZone getTimeZone  UTC                    Locale getDefault             TimeZone tz   cal getTimeZone             cal setTime localTime            timeStamp    localTime getTime   1000           Log d  GMT TimeStamp       Date TimegmtTime      datetime                      GMT TimeStamp       localTime getTime            catch  Exception e               TODO Auto-generated catch block         e printStackTrace               return timeStamp       It will return the UTC time based on passed date    We can do reverse like UTC time stamp to current date and time vice versa        public static String getLocalTimeFromGMT long gmtTimeStamp                 try                      Calendar calendar   Calendar getInstance                        TimeZone tz   TimeZone getDefault                        calendar setTimeInMillis gmtTimeStamp   1000                       calendar add Calendar MILLISECOND  tz getOffset calendar getTimeInMillis                           SimpleDateFormat sdf   new SimpleDateFormat  dd-MM-yyyy HH mm ss                        Date currenTimeZone    Date  calendar getTime                        return sdf format currenTimeZone                    catch  Exception e                                      return                        I hope this will help others  Thanks

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To find duration or time interval with two different time zone   import org joda time  DateTime  Period  PeriodType   val s1    2019-06-13T05 50 00-07 00  val s2    2019-10-09T11 30 00 09 00       val period   new Period DateTime parse s1   DateTime parse s2   PeriodType dayTime     period getDays period getMinutes period getHours   output     period   P117DT13H40M  days   117 minutes   40 hours   13

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tl dr  Instant ofEpochMilli  1 317 816 735 000L        atZone  ZoneId of   Pacific Auckland           format  DateTimeFormatter ofLocalizedDateTime  FormatStyle MEDIUM   withLocale  new Locale   en     NZ             also     LocalDateTime parse   2011-10-06 03 35 05  replace         T           atZone  ZoneId of   Pacific Auckland        java time  The Question and most Answers use outdated legacy date-time classes from the earliest versions of Java  These old classes have proven to be troublesome and confusing  Avoid them  Instead use the java time classes   ISO 8601  Your input string is nearly in standard ISO 8601 format  Just replace the SPACE in the middle with a T    String input    2011-10-06 03 35 05  replace         T       LocalDateTime  Now parse as a LocalDateTime because the input lacks any information about offset-from-UTC or time zone  A LocalDateTime has no concept of offset nor time zone  so it does not represent an actual moment on the timeline   LocalDateTime ldt   LocalDateTime parse  input      ZoneOffset  You seem to be saying that from the business context you know the intention of this string is to represent a moment that is 13 hours ahead of UTC  So we instantiate a ZoneOffset   ZoneOffset offset   ZoneOffset ofHours  13       13 hours ahead of UTC  in the far east of the globe    OffsetDateTime  Apply it to get an OffsetDateTime object  This becomes an actual moment on the timeline   OffsetDateTime odt   ldt atOffset  offset     ZoneId  But then you mention New Zealand  So you had a specific time zone in mind  A time zone is an offset-from-UTC plus a set of rules for handling anomalies such as Daylight Saving Time  DST   So we can specify a ZoneId to a ZonedDateTime rather than a mere offset    Specify a proper time zone name  Never use the 3-4 letter abbreviation such as EST or IST as they are not true time zones  not standardized  and not even unique     For example  Pacific Auckland   ZoneId z   ZoneId of   Pacific Auckland       ZonedDateTime  Apply the ZoneId   ZonedDateTime zdt   ldt atZone  z      You can easily adjust into another zone for the very same moment on the timeline   ZoneId zParis   ZoneId of   Europe Paris     ZonedDateTime zdtParis   zdt withZoneSameInstant  zParis        Same moment in time  but seen through lens of Paris wall-clock time    Count from epoch  I strongly recommend against handling date-time values as a count from epoch  such as milliseconds from the start of 1970 UTC  But if you must  create a Instant from such a number   Instant instant   Instant ofEpochMilli  1 317 816 735 000L      Then assign a time zone as seen above  if desired  to move away from UTC   ZoneId z   ZoneId of   Pacific Auckland     ZonedDateTime zdt   instant atZone  z      Your value of 1 317 816 735 000L is    2011-10-05T12 12 15Z  Wed  05 Oct 2011 12 12 15 GMT  2011-10-06T01 12 15 13 00 Pacific Auckland   Thursday October 06  2011 01 12 15 in Auckland New Zealand     Generate strings  To generate a string in standard ISO 8601 format  simply call toString  Note that ZonedDateTime wisely extends the standard format by appending the name of the time zone in square brackets   String output   zdt toString      For other formats  search Stack Overflow for DateTimeFormatter class  Already covered many times    Specify a FormatStyle and a Locale   Locale l   new Locale   en     NZ     DateTimeFormatter f   DateTimeFormatter ofLocalizedDateTime  FormatStyle MEDIUM   withLocale  l    String output   zdt format  f      Note that time zone has nothing to do with locale  You can have a Europe Paris date-time displayed in Japanese language  amp  cultural norms  or a Asia Kolkata date-time displayed in Portuguese language and Brazil cultural norms   About java time  The java time framework is built into Java 8 and later  These classes supplant the troublesome old date-time classes such as java util Date   Calendar   amp  java text SimpleDateFormat    The Joda-Time project  now in maintenance mode  advises migration to java time   To learn more  see the Oracle Tutorial  And search Stack Overflow for many examples and explanations   Much of the java time functionality is back-ported to Java 6  amp  7 in ThreeTen-Backport and further adapted to Android in ThreeTenABP  see How to use       The ThreeTen-Extra project extends java time with additional classes  This project is a proving ground for possible future additions to java time  You may find some useful classes here such as Interval  YearWeek  YearQuarter  and more

User · Answer

Understanding how computer time works is very important  With that said I agree that if an API is created to help you process computer time like real time then it should work in such a way that allows you to treat it like real time  For the most part this is the case but there are some major oversights which do need attention   Anyway I digress   If you have your UTC offset  better to work in UTC than GMT offsets  you can calculate the time in milliseconds and add that to your timestamp  Note that an SQL Timestamp may vary from a Java timestamp as the way the elapse from the epoch is calculated is not always the same - dependant on database technologies and also operating systems   I would advise you to use System currentTimeMillis   as your time stamps as these can be processed more consistently in java without worrying about converting SQL Timestamps to java Date objects etc   To calculate your offset you can try something like this   Long gmtTime  1317951113613L     2 32pm NZDT Long timezoneAlteredTime   0L   if  offset    0L        int multiplier    offset 60   60 1000       timezoneAlteredTime   gmtTime   multiplier    else       timezoneAlteredTime   gmtTime     Calendar calendar   new GregorianCalendar    calendar setTimeInMillis timezoneAlteredTime    DateFormat formatter   new SimpleDateFormat  dd MMM yyyy HH mm ss z     formatter setCalendar calendar   formatter setTimeZone TimeZone getTimeZone timeZone     String newZealandTime   formatter format calendar getTime       I hope this is helpful

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I have try this code   try              SimpleDateFormat sdf   new SimpleDateFormat  dd-MM-yyyy hh mm ss Z                Date datetime   new Date                 System out println  date   sdf format datetime                 sdf setTimeZone TimeZone getTimeZone  GMT                  System out println  GMT    sdf format datetime                 sdf setTimeZone TimeZone getTimeZone  GMT 13                  System out println  GMT 13    sdf format datetime                 sdf setTimeZone TimeZone getTimeZone  UTC                  System out println  utc   sdf format datetime                 Calendar calendar   new GregorianCalendar TimeZone getTimeZone  GMT                  DateFormat formatter   new SimpleDateFormat  dd MMM yyyy HH mm ss z                    formatter setTimeZone TimeZone getTimeZone  GMT 13                    String newZealandTime   formatter format calendar getTime                  System out println  using calendar   newZealandTime             catch  Exception e                   TODO Auto-generated catch block             e printStackTrace                and getting this result  date 06-10-2011 10 40 05  0530 GMT 06-10-2011 05 10 05  0000    here getting 5 10 05 GMT 13 06-10-2011 06 10 05  1300    here getting 6 10 05 utc 06-10-2011 05 10 05  0000 using calendar 06 Oct 2011 18 10 05 GMT 13 00

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I should like to provide the modern answer   You shouldn   t really want to convert a date and time from a string at one GMT offset to a string at a different GMT offset and with in a different format  Rather in your program keep an instant  a point in time  as a proper date-time object  Only when you need to give string output  format your object into the desired string   java time  Parsing input      DateTimeFormatter formatter   new DateTimeFormatterBuilder                append DateTimeFormatter ISO LOCAL DATE               appendLiteral                   append DateTimeFormatter ISO LOCAL TIME               toFormatter         String dateTimeString    2011-10-06 03 35 05       Instant instant   LocalDateTime parse dateTimeString  formatter               atOffset ZoneOffset UTC               toInstant      For most purposes Instant is a good choice for storing a point in time  If you needed to make it explicit that the date and time came from GMT  use an OffsetDateTime instead   Converting  formatting and printing output      ZoneId desiredZone   ZoneId of  Pacific Auckland        Locale desiredeLocale   Locale forLanguageTag  en-NZ        DateTimeFormatter desiredFormatter   DateTimeFormatter ofPattern               dd MMM uuuu HH mm ss OOOO   desiredeLocale        ZonedDateTime desiredDateTime   instant atZone desiredZone       String result   desiredDateTime format desiredFormatter       System out println result     This printed      06 Oct 2011 16 35 05 GMT 13 00   I specified time zone Pacific Auckland rather than the offset you mentioned   13 00  I understood that you wanted New Zealand time  and Pacific Auckland better tells the reader this  The time zone also takes summer time  DST  into account so you don   t need to take this into account in your own code  for most purposes    Since Oct is in English  it   s a good idea to give the formatter an explicit locale  GMT might be localized too  but I think that it just prints GMT in all locales   OOOO in the format patterns string is one way of printing the offset  which may be a better idea than printing the time zone abbreviation you would get from z since time zone abbreviations are often ambiguous  If you want NZDT  for New Zealand Daylight Time   just put z there instead   Your questions  I will answer your numbered questions in relation to the modern classes in java time      Is possible to          Set the time on an object      No  the modern classes are immutable  You need to create an object that has the desired date and time from the outset  this has a number of advantages including thread safety           Possibly  Set the TimeZone of the initial time stamp      The atZone method that I use in the code returns a ZonedDateTime with the specified time zone  Other date-time classes have a similar method  sometimes called atZoneSameInstant or other names         Format the time stamp with a new TimeZone      With java time converting to a new time zone and formatting are two distinct steps as shown         Return a string with new time zone time       Yes  convert to the desired time zone as shown and format as shown      I found that anytime I try to set the time like this   calendar setTime new Date 1317816735000L          the local machine s TimeZone is used  Why is that    It   s not the way you think  which goes nicely to show just a couple of the  many  design problems with the old classes    A Date hasn   t got a time zone  Only when you print it  its toString method grabs your local time zone and uses it for rendering the string  This is true for new Date   too  This behaviour has confused many  many programmers over the last 25 years  A Calender has got a time zone  It doesn   t change when you do calendar setTime new Date 1317816735000L       Link  Oracle tutorial  Date Time explaining how to use java time

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Had a look about and I don t think theres a timezone in Java that is GMT   13  So I think you have to use    Calendar calendar   Calendar getInstance      OR Calendar getInstance TimeZone getTimeZone  GMT      calendar set Calendar HOUR OF DAY  calendar get Calendar HOUR OF DAY  13    Date d   calendar getTime       If there is then change  GMT  to that Timezone and remove the 2nd line of code   OR  SimpleDateFormat df   new SimpleDateFormat    df setTimeZone TimeZone getTimeZone  GMT 13     System out println df format c getTime        If you want to set a specific time date you can also use       calendar set Calendar DATE  15   calendar set Calendar MONTH  3   calendar set Calendar YEAR  2011   calendar set Calendar HOUR OF DAY  13    calendar set Calendar MINUTE  45   calendar set Calendar SECOND  00

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A quick way is    String dateText   Thu  02 Jul 2015 21 51 46   long hours   -5     time difference between places  DateTimeFormatter formatter   DateTimeFormatter ofPattern E  dd MMM yyyy HH mm ss  Locale ENGLISH        LocalDateTime date   LocalDateTime parse dateText  formatter           date   date with date plusHours hours     System out println  NEW DATE    date     Output  NEW DATE  2015-07-02T16 51 46

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We can handle this by using offset value   public static long convertDateTimeZone long lngDate  String fromTimeZone          String toTimeZone       TimeZone toTZ   TimeZone getTimeZone toTimeZone       Calendar toCal   Calendar getInstance toTZ                TimeZone fromTZ   TimeZone getTimeZone fromTimeZone       Calendar fromCal   Calendar getInstance fromTZ       fromCal setTimeInMillis lngDate       toCal setTimeInMillis fromCal getTimeInMillis                 toTZ getOffset fromCal getTimeInMillis                - TimeZone getDefault   getOffset fromCal getTimeInMillis                return toCal getTimeInMillis        Test Code snippet    System out println new Date   getTime     System out println convertDateTimeZone new Date   getTime    TimeZone                  getDefault   getID     EST       Output      1387353270742     1387335270742

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The solution is actually quite simple  pure  simple Java    System out println   NZ Local Time  2011-10-06 03 35 05    DateTimeFormatter formatter   DateTimeFormatter ofPattern  yyyy-MM-dd HH mm ss    LocalDateTime localNZ   LocalDateTime parse  2011-10-06 03 35 05  formatter   ZonedDateTime zonedNZ   ZonedDateTime of localNZ ZoneId of   13 00     LocalDateTime localUTC   zonedNZ withZoneSameInstant ZoneId of  UTC    toLocalDateTime    System out println  UTC Local Time    localUTC format formatter      OUTPUT IS    NZ Local Time  2011-10-06 03 35 05 UTC Local Time  2011-10-05 14 35 05

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display date and time for all timezones  import java util Calendar  import java util TimeZone  import java text DateFormat  import java text SimpleDateFormat     static final String ISO8601    yyyy-MM-dd T HH mm ssZ   DateFormat dateFormat   new SimpleDateFormat ISO8601   Calendar c   Calendar getInstance    String formattedTime  for  String availableID   TimeZone getAvailableIDs          dateFormat setTimeZone TimeZone getTimeZone availableID        formattedTime   dateFormat format c getTime         System out println formattedTime         availableID

[java] Convert Date/Time for given Timezone - java

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