Difference in days between two dates in Java

Question

I need to find the number of days between two dates  one is from a report and one is the current date  My snippet     int age calculateDifference agingDate  today     Here calculateDifference is a private method  agingDate and today are Date objects  just for your clarification  I ve followed two articles from a Java forum  Thread 1   Thread 2    It works fine in a standalone program although when I include this into my logic to read from the report I get an unusual difference in values    Why is it happening and how can I fix it   EDIT    I m getting a greater number of days compared to the actual amount of Days   public static int calculateDifference Date a  Date b        int tempDifference   0      int difference   0      Calendar earlier   Calendar getInstance        Calendar later   Calendar getInstance         if  a compareTo b   lt  0                earlier setTime a           later setTime b             else               earlier setTime b           later setTime a              while  earlier get Calendar YEAR     later get Calendar YEAR                 tempDifference   365    later get Calendar YEAR  - earlier get Calendar YEAR            difference    tempDifference           earlier add Calendar DAY OF YEAR  tempDifference              if  earlier get Calendar DAY OF YEAR     later get Calendar DAY OF YEAR                 tempDifference   later get Calendar DAY OF YEAR  - earlier get Calendar DAY OF YEAR           difference    tempDifference           earlier add Calendar DAY OF YEAR  tempDifference              return difference      Note    Unfortunately  none of the answers helped me solve the problem  I ve accomplished this problem with the help of Joda-time library

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ThreeTen-Extra

The Answer by Vitalii Fedorenko is correct, describing how to perform this calculation in a modern way with java.time classes (Duration & ChronoUnit) built into Java 8 and later (and back-ported to Java 6 & 7 and to Android).

`Days`

If you are using a number of days routinely in your code, you can replace mere integers with use of a class. The Days class can be found in the ThreeTen-Extra project, an extension of java.time and proving ground for possible future additions to java.time. The Days class provides a type-safe way of representing a number of days in your application. The class includes convenient constants for ZERO and ONE.

Given the old outmoded java.util.Date objects in the Question, first convert them to modern java.time.Instant objects. The old date-time classes have newly added methods to facilitate conversion to java.time, such a java.util.Date::toInstant.

Instant start = utilDateStart.toInstant(); // Inclusive.
Instant stop = utilDateStop.toInstant();  // Exclusive.

Pass both Instant objects to factory method for org.threeten.extra.Days.

In the current implementation (2016-06) this is a wrapper calling java.time.temporal.ChronoUnit.DAYS.between, read the ChronoUnit class doc for details. To be clear: all uppercase DAYS is in the enum ChronoUnit while initial-cap Days is a class from ThreeTen-Extra.

Days days = Days.between( start , stop );

You can pass these Days objects around your own code. You can serialize to a String in the standard ISO 8601 format by calling toString. This format of PnD uses a P to mark the beginning and D means “days”, with a number of days in between. Both java.time classes and ThreeTen-Extra use these standard formats by default when generating and parsing Strings representing date-time values.

String output = days.toString();

P3D

Days days = Days.parse( "P3D" );

User · Answer

This code calculates days between 2 date Strings       static final long MILLI SECONDS IN A DAY   1000   60   60   24      static final String DATE FORMAT    dd-MM-yyyy       public long daysBetween String fromDateStr  String toDateStr  throws ParseException       SimpleDateFormat format   new SimpleDateFormat DATE FORMAT       Date fromDate      Date toDate      fromDate   format parse fromDateStr       toDate   format parse toDateStr       return  toDate getTime   - fromDate getTime      MILLI SECONDS IN A DAY

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You should use Joda Time library because Java Util Date returns wrong values sometimes   Joda vs Java Util Date  For example  days between yesterday  dd-mm-yyyy  12-07-2016  and first day of year in 1957  dd-mm-yyyy  01-01-1957    public class Main    public static void main String   args        SimpleDateFormat format   new SimpleDateFormat  dd-MM-yyyy         Date date   null      try           date   format parse  12-07-2016          catch  ParseException e            e printStackTrace                 Try with Joda - prints 21742     System out println  This is correct      getDaysBetweenDatesWithJodaFromYear1957 date          Try with Java util - prints 21741     System out println  This is not correct      getDaysBetweenDatesWithJavaUtilFromYear1957 date            private static int getDaysBetweenDatesWithJodaFromYear1957 Date date        DateTime jodaDateTime   new DateTime date       DateTimeFormatter formatter   DateTimeFormat forPattern  dd-MM-yyyy        DateTime y1957   formatter parseDateTime  01-01-1957         return Days daysBetween y1957   jodaDateTime  getDays       private static long getDaysBetweenDatesWithJavaUtilFromYear1957 Date date        SimpleDateFormat format   new SimpleDateFormat  dd-MM-yyyy         Date y1957   null      try           y1957   format parse  01-01-1957          catch  ParseException e            e printStackTrace               return TimeUnit DAYS convert date getTime   - y1957 getTime    TimeUnit MILLISECONDS       So I really advice you to use Joda Time library

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The diff    24   etc  does not take Timezone into account  so if your default timezone has a DST in it  it can throw the calculation off   This link has a nice little implementation   Here is the source of the above link in case the link goes down       Using Calendar - THE CORRECT WAY      public static long daysBetween Calendar startDate  Calendar endDate          assert  startDate must be before endDate     Calendar date    Calendar  startDate clone        long daysBetween   0      while  date before endDate           date add Calendar DAY OF MONTH  1         daysBetween              return daysBetween          and      Using Calendar - THE CORRECT   amp  Faster  WAY      public static long daysBetween final Calendar startDate  final Calendar endDate        assert  startDate must be before endDate     int MILLIS IN DAY   1000   60   60   24      long endInstant   endDate getTimeInMillis        int presumedDays         int    endInstant - startDate getTimeInMillis      MILLIS IN DAY       Calendar cursor    Calendar  startDate clone        cursor add Calendar DAY OF YEAR  presumedDays       long instant   cursor getTimeInMillis        if  instant    endInstant        return presumedDays     final int step   instant  lt  endInstant   1   -1      do         cursor add Calendar DAY OF MONTH  step         presumedDays    step        while  cursor getTimeInMillis      endInstant       return presumedDays

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Based on  Mad Troll s answer  I developed this method   I ve run about 30 test cases against it  is the only method that handles sub day time fragments correctly   Example  If you pass now  amp  now   1 millisecond that is still the same day  Doing 1-1-13 23 59 59 098 to 1-1-13 23 59 59 099 returns 0 days  correctly  allot of the other methods posted here will not do this correctly   Worth noting it does not care about which way you put them in  If your end date is before your start date it will count backwards          This is not quick but if only doing a few days backwards forwards then it is very accurate         param startDate from     param endDate   to     return day count between the two dates  this can be negative if startDate is after endDate     public static long daysBetween  NotNull final Calendar startDate   NotNull final Calendar endDate           Forwards or backwards      final boolean forward   startDate before endDate          Which direction are we going     final int multiplier   forward   1   -1          The date we are going to move      final Calendar date    Calendar  startDate clone            Result     long daysBetween   0          Start at millis  then bump up until we go back a day      int fieldAccuracy   4      int field      int dayBefore  dayAfter      while  forward  amp  amp  date before endDate      forward  amp  amp  endDate before date                We start moving slowly if no change then we decrease accuracy          switch  fieldAccuracy                case 4                  field   Calendar MILLISECOND                  break              case 3                  field   Calendar SECOND                  break              case 2                  field   Calendar MINUTE                  break              case 1                  field   Calendar HOUR OF DAY                  break              default              case 0                  field   Calendar DAY OF MONTH                  break                       Get the day before we move the time  Change  then get the day after          dayBefore   date get Calendar DAY OF MONTH           date add field  multiplier           dayAfter   date get Calendar DAY OF MONTH               This shifts lining up the dates  one field at a time          if  dayBefore    dayAfter  amp  amp  date get field     endDate get field               fieldAccuracy--             If day has changed after moving at any accuracy level we bump the day counter          if  dayBefore    dayAfter                daysBetween    multiplier                      return daysBetween      You can remove the  NotNull annotations  these are used by Intellij to do code analysis on the fly

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I use this funcion    DATEDIFF  31 01 2016    01 03 2016      me return 30 days   my function   import java util Date   public long DATEDIFF String date1  String date2            long MILLISECS PER DAY   24   60   60   1000          long days   0l          SimpleDateFormat format   new SimpleDateFormat  dd MM yyyy        dd MM yyyy HH mm ss             Date dateIni   null          Date dateFin   null                  try                      dateIni    Date  format parse date1               dateFin    Date  format parse date2               days    dateFin getTime   - dateIni getTime    MILLISECS PER DAY                                    catch  Exception e     e printStackTrace                   return days

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Look at the getFragmentInDays methods in this apache commons-lang class DateUtils

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You say it  works fine in a standalone program   but that you get  unusual difference values  when you  include this into my logic to read from report    That suggests that your report has some values for which it doesn t work correctly  and your standalone program doesn t have those values   Instead of a standalone program  I suggest a test case   Write a test case much as you would a standalone program  subclassing from JUnit s TestCase class   Now you can run a very specific example  knowing what value you expect  and don t give it today for the test value  because today changes over time    If you put in the values you used in the standalone program  your tests will probably pass   That s great - you want those cases to keep working   Now  add a value from your report  one that doesn t work right   Your new test will probably fail   Figure out why it s failing  fix it  and get to green  all tests passing    Run your report   See what s still broken  write a test  make it pass   Pretty soon you ll find your report is working

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public static int getDifferenceIndays long timestamp1  long timestamp2        final int SECONDS   60      final int MINUTES   60      final int HOURS   24      final int MILLIES   1000      long temp      if  timestamp1  lt  timestamp2            temp   timestamp1          timestamp1   timestamp2          timestamp2   temp            Calendar startDate   Calendar getInstance TimeZone getDefault         Calendar endDate   Calendar getInstance TimeZone getDefault         endDate setTimeInMillis timestamp1       startDate setTimeInMillis timestamp2       if   timestamp1 - timestamp2   lt  1   HOURS   MINUTES   SECONDS   MILLIES            int day1   endDate get Calendar DAY OF MONTH           int day2   startDate get Calendar DAY OF MONTH           if  day1    day2                return 0            else               return 1                      int diffDays   0      startDate add Calendar DAY OF MONTH  diffDays       while  startDate before endDate             startDate add Calendar DAY OF MONTH  1           diffDays              return diffDays

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I did it this way  it s easy     Date d1   jDateChooserFrom getDate    Date d2   jDateChooserTo getDate     Calendar day1   Calendar getInstance    day1 setTime d1    Calendar day2   Calendar getInstance    day2 setTime d2    int from   day1 get Calendar DAY OF YEAR   int to   day2 get Calendar DAY OF YEAR    int difference   to-from

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import java util Calendar  import java util Date   public class Main       public static long calculateDays String startDate  String endDate                Date sDate   new Date startDate           Date eDate   new Date endDate           Calendar cal3   Calendar getInstance            cal3 setTime sDate           Calendar cal4   Calendar getInstance            cal4 setTime eDate           return daysBetween cal3  cal4              public static void main String   args            System out println calculateDays  2012 03 31    2012 06 17                     Using Calendar - THE CORRECT WAY        public static long daysBetween Calendar startDate  Calendar endDate            Calendar date    Calendar  startDate clone            long daysBetween   0          while  date before endDate                 date add Calendar DAY OF MONTH  1               daysBetween                      return daysBetween

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It depends on what you define as the difference  To compare two dates at midnight you can do   long day1           in milliseconds  long day2           in milliseconds  long days    day2 - day1    86400000

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Solution using difference between milliseconds time  with correct rounding for DST dates   public static long daysDiff Date from  Date to        return daysDiff from getTime    to getTime        public static long daysDiff long from  long to        return Math round   to - from    86400000D       1000   60   60   24     One note  Of course  dates must be in some timezone   The important code   Math round   to - from    86400000D     If you don t want round  you can use UTC dates

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Hundred lines of code for this basic function     Just a simple method   protected static int calculateDayDifference Date dateAfter  Date dateBefore       return  int  dateAfter getTime  -dateBefore getTime     1000   60   60   24           MILLIS IN DAY   1000   60   60   24

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java time  In Java 8 and later  use the java time framework  Tutorial    Duration  The Duration class represents a span of time as a number of seconds plus a fractional second  It can count days  hours  minutes  and seconds   ZonedDateTime now   ZonedDateTime now    ZonedDateTime oldDate   now minusDays 1  minusMinutes 10   Duration duration   Duration between oldDate  now   System out println duration toDays       ChronoUnit  If all you need is the number of days  alternatively you can use the ChronoUnit enum  Notice the calculation methods return a long rather than int   long days   ChronoUnit DAYS between  then  now

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Illustration of the problem   My code is computing delta in weeks  but same issue applies with delta in days   Here is a very reasonable-looking implementation   public static final long MILLIS PER WEEK   7L   24L   60L   60L   1000L   static public int getDeltaInWeeks Date latterDate  Date earlierDate        long deltaInMillis   latterDate getTime   - earlierDate getTime        int deltaInWeeks    int  deltaInMillis   MILLIS PER WEEK       return deltaInWeeks       But this test will fail   public void testGetDeltaInWeeks         delta   AggregatedData getDeltaInWeeks dateMar09  dateFeb23       assertEquals  weeks between Feb23 and Mar09   2  delta       The reason is      Mon Mar 09 00 00 00 EDT 2009   1 236 571 200 000 Mon Feb 23   00 00 00 EST 2009   1 235 365 200 000 MillisPerWeek     604 800 000 Thus   Mar09 - Feb23    MillisPerWeek     1 206 000 000   604 800 000   1 994      but anyone looking at a calendar would agree that the answer is 2

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If you re looking for a solution that returns proper number or days between e g  11 30 2014 23 59 and 12 01 2014 00 01 here s solution using Joda Time    private int getDayDifference long past  long current        DateTime currentDate   new DateTime current       DateTime pastDate   new DateTime past       return currentDate getDayOfYear   - pastDate getDayOfYear         This implementation will return 1 as a difference in days  Most of the solutions posted here calculate difference in milliseconds between two dates  It means that 0 would be returned because there s only 2 minutes difference between these two dates

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I might be too late to join the game but what the heck huh      Do you think this is a threading issue  How are you using the output of this method for example  OR  Can we change your code to do something as simple as   Calendar calendar1   Calendar getInstance        Calendar calendar2   Calendar getInstance        calendar1 set  lt your earlier date gt        calendar2 set  lt your current date gt        long milliseconds1   calendar1 getTimeInMillis        long milliseconds2   calendar2 getTimeInMillis        long diff   milliseconds2 - milliseconds1      long diffSeconds   diff   1000      long diffMinutes   diff    60   1000       long diffHours   diff    60   60   1000       long diffDays   diff    24   60   60   1000       System out println   nThe Date Different Example        System out println  Time in milliseconds      diff      milliseconds         System out println  Time in seconds      diffSeconds      seconds         System out println  Time in minutes      diffMinutes      minutes         System out println  Time in hours      diffHours      hours         System out println  Time in days      diffDays      days

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I would suggest you use the excellent Joda Time library instead of the flawed java util Date and friends   You could simply write  import java util Date  import org joda time DateTime  import org joda time Days   Date past   new Date 110  5  20      June 20th  2010 Date today   new Date 110  6  24      July 24th  int days   Days daysBetween new DateTime past   new DateTime today   getDays         gt  34

[java] Difference in days between two dates in Java?

ThreeTen-Extra

`Days`

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