Converting Long to Date in Java returns 1970

Question

I have list with long values  for example  1220227200  1220832000  1221436800     which I downloaded from web service  I must convert it to Dates  Unfortunately this way  for example   Date d   new Date 1220227200     returns 1 Jan 1970  Anyone know another way to convert it correctly

User · Answer

Try this   Calendar cal   Calendar getInstance    cal setTimeInMillis 1220227200   1000   System out println cal getTime

User · Answer

Works for me  You probably want to multiplz it with 1000  since what you get are the seconds from 1970 and you have to pass the milliseconds from jan 1 1970

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Only set the time in mills on Calendar  object  Calendar c   Calendar getInstance    c setTimeInMillis 1385355600000l   System out println c get Calendar YEAR    System out println c get Calendar MONTH    System out println c get Calendar DAY OF MONTH       get Date System out println c getTime

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tl dr java time Instant                       Represent a moment as seen in UTC  Internally  a count of nanoseconds since 1970-01-01T00 00Z   ofEpochSecond  1 220 227 200L          Pass a count of whole seconds since the same epoch reference of 1970-01-01T00 00Z   Know Your Data People use various precisions in tracking time as a number since an epoch  So when you obtain some numbers to be interpreted as a count since an epoch  you must determine   What epoch Many epochs dates have been used in various systems  Commonly used is POSIX Unix time  where the epoch is the first moment of 1970 in UTC  But you should not assume this epoch  What precision Are we talking seconds  milliseconds  microseconds  or nanoseconds since the epoch  What time zone Usually a count since epoch is in UTC GMT time zone  that is  has no time zone offset at all  But sometimes  when involving inexperienced or date-time ignorant programmers  there may be an implied time zone   In your case  as others noted  you seem to have been given seconds since the Unix epoch  But you are passing those seconds to a constructor that expects milliseconds  So the solution is to multiply by 1 000  Lessons learned   Determine  don t assume  the meaning of received data  Read the doc    Your Data Your data seems to be in whole seconds  If we assume an epoch of the beginning of 1970  and if we assume UTC time zone  then 1 220 227 200 is the first moment of the first day of September 2008  Joda-Time The java util Date and  Calendar classes bundled with Java are notoriously troublesome  Avoid them  Use instead either the Joda-Time library or the new java time package bundled in Java 8  and inspired by Joda-Time   Note that unlike j u Date  a DateTime in Joda-Time truly knows its own assigned time zone  So in the example Joda-Time 2 4 code seen below  note that we first parse the milliseconds using the default assumption of UTC  Then  secondly  we assign a time zone of Paris to adjust  Same moment in the timeline of the Universe  but different wall-clock time  For demonstration  we adjust again  to UTC  Almost always better to explicitly specify your desired expected time zone rather than rely on an implicit default  often the cause of trouble in date-time work   We need milliseconds to construct a DateTime  So take your input of seconds  and multiply by a thousand  Note that the result must be a 64-bit long as we would overflow a 32-bit int  long input   1 220 227 200L      Note the  quot L quot  appended to long integer literals  long milliseconds     input   1 000L       Use a  quot long quot   not the usual  quot int quot   Note the appended  quot L quot    Feed that count of milliseconds to constructor  That particular constructor assumes the count is from the Unix epoch of 1970  So adjust time zone as desired  after construction  Use proper time zone names  a combination of continent and city region  Never use 3 or 4 letter codes such as EST as they are neither standardized not unique  DateTime dateTimeParis   new DateTime  milliseconds   withZone  DateTimeZone forID   quot Europe Paris quot        For demonstration  adjust the time zone again  DateTime dateTimeUtc   dateTimeParis withZone  DateTimeZone UTC    DateTime dateTimeMontr  al   dateTimeParis withZone  DateTimeZone forID   quot America Montreal quot        Dump to console  Note how the date is different in Montr  al  as the new day has begun in Europe but not yet in America  System out println   quot dateTimeParis   quot    dateTimeParis    System out println   quot dateTimeUTC   quot    dateTimeUtc    System out println   quot dateTimeMontr  al   quot    dateTimeMontr  al     When run  dateTimeParis  2008-09-01T02 00 00 000 02 00 dateTimeUTC  2008-09-01T00 00 00 000Z dateTimeMontr  al  2008-08-31T20 00 00 000-04 00  java time The makers of Joda-Time have asked us to migrate to its replacement  the java time framework as soon as is convenient  While Joda-Time continues to be actively supported  all future development will be done on the java time classes and their extensions in the ThreeTen-Extra project  The java-time framework is defined by JSR 310 and built into Java 8 and later  The java time classes have been back-ported to Java 6  amp  7 on the ThreeTen-Backport project and to Android in the ThreeTenABP project  An Instant is a moment on the timeline in UTC with a resolution of nanoseconds  Its epoch is the first moment of 1970 in UTC  Instant instant   Instant ofEpochSecond  1 220 227 200L     Apply an offset-from-UTC ZoneOffset to get an OffsetDateTime  Better yet  if known  apply a time zone ZoneId to get a ZonedDateTime  ZoneId zoneId   ZoneId of   quot America Montreal quot     ZonedDateTime zdt   ZonedDateTime ofInstant  instant   zoneId

User · Answer

The long values  most likely  correspond to Epoch timestamps  and the values are   1220227200   Mon  01 Sep 2008 00 00 00 GMT  1220832000   Mon  08 Sep 2008 00 00 00 GMT  1221436800   Mon  15 Sep 2008 00 00 00 GMT  One can convert these long values to java util Date  taking into account the fact java util Date uses millisecs     as previously hinted  but with some flaw - like this      note  enforcing long literals  L   without it the values would just be wrong  Date date   new Date 1220227200L   1000L      Now  to display the date correctly  one can use java text DateFormat as illustrated hereafter   DateFormat df   DateFormat getDateTimeInstance DateFormat FULL  DateFormat FULL   df setTimeZone TimeZone getTimeZone  UTC     System out println  Wrong date time value      date   System out println  Correct date time value      df format date      Below are the results of displaying the converted long value to java util Date without  using and using the DateFormat   Date wrong  off by 2 hours   Mon Sep 01 02 00 00 CEST 2008 Correct date   Monday  1 September 2008 00 00 00 o clock UTC

User · Answer

New Date number  returns a date that s number milliseconds after 1 Jan 1970   Odds are you date format isn t showing hours  minutes  and seconds for you to see that it s just a little bit after 1 Jan 1970   You need to parse the date according to the correct parsing routing   I don t know what a 1220227200 is  but if it s seconds after 1 JAN 1970  then multiply it to yield milliseconds   If it is not  then convert it in some manner to milliseconds after 1970  if you want to continue to use java util Date

User · Answer

Those are probably timestamps in seconds and not in milliseconds which is required for the java new Date long  constructor  Just multiply them by 1000 and you should be allright

User · Answer

1220227200 corresponds to Jan 15 1980  and indeed new Date 1220227200  toString   returns  Thu Jan 15 03 57 07 CET 1970    If you pass a long value to a date  that is before 01 01 1970 it will in fact return a date of 01 01 1970  Make sure that your values are not in this situation  lower than 82800000

User · Answer

It looks like your longs are seconds  and not milliseconds  Date constructor takes time as millis  so   Date d   new Date timeInSeconds   1000

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The Date constructor  click the link   accepts the time as long in milliseconds  not seconds  You need to multiply it by 1000 and make sure that you supply it as long   Date d   new Date 1220227200L   1000     This shows here     Sun Aug 31 20 00 00 GMT-04 00 2008

User · Answer

Try this with adjusting the date format   long longtime   1212580300  SimpleDateFormat dateFormat   new SimpleDateFormat  MMddyyHHmm    Date date    Date  dateFormat parseObject longtime        System out println date     Note  Check for 24 hours or 12 hours cycle

[java] Converting Long to Date in Java returns 1970

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