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) < 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.

Answer 1

I've already written about it. This is a repost from Calculating the difference between two Java date instances.

public int getDiffernceInDays(long timeAfter, long timeBefore) {
    Calendar calendarAfter = Calendar.getInstance();
    calendarAfter.setTime(new Date(timeAfter));

    Calendar calendarNewAfter = Calendar.getInstance();
    calendarNewAfter.set(calendarAfter.get(Calendar.YEAR), calendarAfter.get(Calendar.MONTH), calendarAfter.get(Calendar.DAY_OF_MONTH));

    Calendar calendarBefore = Calendar.getInstance();
    calendarBefore.setTime(new Date(timeBefore));

    Calendar calendarNewBefore = Calendar.getInstance();
    calendarNewBefore.set(calendarBefore.get(Calendar.YEAR), calendarBefore.get(Calendar.MONTH), calendarBefore.get(Calendar.DAY_OF_MONTH));

    return (int) ((calendarNewAfter.getTime().getTime() - calendarNewBefore.getTime().getTime()) / (24 * 60 * 60 * 1000));
}

Answer 2

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,

Answer 3

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;
}

Answer 4

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;
    }
}

Answer 5

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;
}

Answer 6

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; 
     }