Adding n hours to a date in Java

Question

How do I add n hours to a Date object   I found another example using days on StackOverflow  but still don t understand how to do it with hours

User · Answer

by using Java 8 classes  we can manipulate date and time very easily as below   LocalDateTime today   LocalDateTime now    LocalDateTime minusHours   today minusHours 24   LocalDateTime minusMinutes   minusHours minusMinutes 30   LocalDate localDate   LocalDate from minusMinutes

User · Answer

To simplify  Christopher s example   Say you have a constant  public static final long HOUR   3600 1000     in milli-seconds    You can write   Date newDate   new Date oldDate getTime     2   HOUR     If you use long to store date time instead of the Date object you can do  long newDate   oldDate   2   HOUR

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Check Calendar class  It has add method  and some others  to allow time manipulation  Something like this should work  Calendar cal   Calendar getInstance       creates calendar cal setTime new Date                      sets calendar time date cal add Calendar HOUR OF DAY  1           adds one hour cal getTime                               returns new date object plus one hour  Check API for more

User · Answer

You can use this method  It is easy to understand and implement    public static java util Date AddingHHMMSSToDate java util Date date  int nombreHeure  int nombreMinute  int nombreSeconde        Calendar calendar   Calendar getInstance        calendar setTime date       calendar add Calendar HOUR OF DAY  nombreHeure       calendar add Calendar MINUTE  nombreMinute       calendar add Calendar SECOND  nombreSeconde       return calendar getTime

User · Answer

Something like   Date oldDate   new Date       oldDate    current time final long hoursInMillis   60L   60L   1000L  Date newDate   new Date oldDate   getTime                               2L   hoursInMillis       Adds 2 hours

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With Joda-Time  DateTime dt   new DateTime    DateTime added   dt plusHours 6

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This is another piece of code when your Date object is in Datetime format  The beauty of this code is  If you give more number of hours the date will also update accordingly       String myString     09 00 12 12 2014       SimpleDateFormat simpleDateFormat   new SimpleDateFormat  HH mm dd MM yyyy        Date myDateTime   null         Parse your string to SimpleDateFormat     try                 myDateTime   simpleDateFormat parse myString               catch  ParseException e                   e printStackTrace                System out println  This is the Actual Date   myDateTime       Calendar cal   new GregorianCalendar        cal setTime myDateTime          Adding 21 Hours to your Date     cal add Calendar HOUR OF DAY  21       System out println  This is Hours Added Date   cal getTime       Here is the Output       This is the Actual Date Fri Dec 12 09 00 00 EST 2014     This is Hours Added Date Sat Dec 13 06 00 00 EST 2014

User · Answer

You can do it with Joda DateTime API  DateTime date  new DateTime dateObj   date   date plusHours 1   dateObj   date toDate

User · Answer

Since Java 8   LocalDateTime now   minusHours 1     See LocalDateTime API

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Date argDate   new Date      set your date  String argTime    09 00     9 AM - 24 hour format  - Set your time  SimpleDateFormat sdf   new SimpleDateFormat  dd-MMM-yyyy    SimpleDateFormat dateFormat   new SimpleDateFormat  dd-MMM-yyyy HH mm    String dateTime   sdf format argDate          argTime  Date requiredDate   dateFormat parse dateTime

User · Answer

You can use the LocalDateTime class from Java 8  For eg    long n   4  LocalDateTime localDateTime   LocalDateTime now    System out println localDateTime plusHours n

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Using the newish java util concurrent TimeUnit class you can do it like this Date oldDate   new Date       oldDate    current time Date newDate   new Date oldDate getTime     TimeUnit HOURS toMillis 2       Add 2 hours

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If you use Apache Commons   Lang  you can do it in one step using DateUtils addHours     Date newDate   DateUtils addHours oldDate  3      The original object is unchanged

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tl dr  myJavaUtilDate toInstant                  plusHours  8     Or     myJavaUtilDate toInstant                     Convert from legacy class to modern class  an  Instant   a point on the timeline in UTC with resolution of nanoseconds                 plus                          Do the math  adding a span of time to our moment  our  Instant                      Duration ofHours  8        Specify a span of time unattached to the timeline                                               Returns another  Instant   Using immutable objects creates a new instance while leaving the original intact    Using java time  The java time framework built into Java 8 and later supplants the old Java util Date  Calendar classes  Those old classes are notoriously troublesome  Avoid them   Use the toInstant method newly added to java util Date to convert from the old type to the new java time type  An Instant is a moment on the time line in UTC with a resolution of nanoseconds   Instant instant   myUtilDate toInstant      You can add hours to that Instant by passing a TemporalAmount such as Duration    Duration duration   Duration ofHours  8    Instant instantHourLater   instant plus  duration      To read that date-time  generate a String in standard ISO 8601 format by calling toString   String output   instantHourLater toString      You may want to see that moment through the lens of some region   s wall-clock time  Adjust the Instant into your desired expected time zone by creating a ZonedDateTime   ZoneId zoneId   ZoneId of   America Montreal     ZonedDateTime zdt   ZonedDateTime ofInstant  instant   zoneId      Alternatively  you can call plusHours to add your count of hours  Being zoned means Daylight Saving Time  DST  and other anomalies will be handled on your behalf   ZonedDateTime later   zdt plusHours  8      You should avoid using the old date-time classes including java util Date and  Calendar  But if you truly need a java util Date for interoperability with classes not yet updated for java time types  convert from ZonedDateTime via Instant  New methods added to the old classes facilitate conversion to from java time types   java util Date date   java util Date from  later toInstant        For more discussion on converting  see my Answer to the Question  Convert java util Date to what    java time    type      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   The Joda-Time project  now in maintenance mode  advises migration to the java time classes   To learn more  see the Oracle Tutorial  And search Stack Overflow for many examples and explanations  Specification is JSR 310   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   Where to obtain the java time classes     Java SE 8  Java SE 9  and later   Built-in   Part of the standard Java API with a bundled implementation  Java 9 adds some minor features and fixes   Java SE 6 and Java SE 7   Much of the java time functionality is back-ported to Java 6  amp  7 in ThreeTen-Backport   Android   Later versions of Android bundle implementations of the java time classes  For earlier Android   lt 26   the ThreeTenABP project adapts ThreeTen-Backport  mentioned above   See How to use ThreeTenABP        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

If you re willing to use java time  here s a method to add ISO 8601 formatted durations   import java time Duration  import java time LocalDateTime        LocalDateTime yourDate                Adds 1 hour to your date   yourDate   yourDate plus Duration parse  PT1H        Java     OR yourDate   yourDate   Duration parse  PT1H       Groovy

[java] Adding n hours to a date in Java?

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