Android/Java - Date Difference in days

Question

I am getting the current date (in format 12/31/1999 i.e. mm/dd/yyyy) as using the below code:

Textview txtViewData;
txtViewDate.setText(\"Today is \" +
              


        

Answer 1

This is NOT my work, found the answer here. did not want a broken link in the future :).

The key is this line for taking daylight setting into account, ref Full Code.

TimeZone.setDefault(TimeZone.getTimeZone("Europe/London"));

or try passing TimeZone as a parameter to daysBetween() and call setTimeZone() in the sDate and eDate objects.

So here it goes:

public static Calendar getDatePart(Date date){
    Calendar cal = Calendar.getInstance();       // get calendar instance
    cal.setTime(date);      
    cal.set(Calendar.HOUR_OF_DAY, 0);            // set hour to midnight
    cal.set(Calendar.MINUTE, 0);                 // set minute in hour
    cal.set(Calendar.SECOND, 0);                 // set second in minute
    cal.set(Calendar.MILLISECOND, 0);            // set millisecond in second
    
    return cal;                                  // return the date part
}

getDatePart() taken from here

/**
 * This method also assumes endDate >= startDate
**/
public static long daysBetween(Date startDate, Date endDate) {
  Calendar sDate = getDatePart(startDate);
  Calendar eDate = getDatePart(endDate);

  long daysBetween = 0;
  while (sDate.before(eDate)) {
      sDate.add(Calendar.DAY_OF_MONTH, 1);
      daysBetween++;
  }
  return daysBetween;
}

The Nuances: Finding the difference between two dates isn't as straightforward as subtracting the two dates and dividing the result by (24 * 60 * 60 * 1000). Infact, its erroneous!

For example: The difference between the two dates 03/24/2007 and 03/25/2007 should be 1 day; However, using the above method, in the UK, you'll get 0 days!

See for yourself (code below). Going the milliseconds way will lead to rounding off errors and they become most evident once you have a little thing like Daylight Savings Time come into the picture.

Full Code:

import java.text.SimpleDateFormat;
import java.util.Calendar;
import java.util.Date;
import java.util.TimeZone;

public class DateTest {

public class DateTest {

static SimpleDateFormat sdf = new SimpleDateFormat("dd-MMM-yyyy");

public static void main(String[] args) {

  TimeZone.setDefault(TimeZone.getTimeZone("Europe/London"));

  //diff between these 2 dates should be 1
  Date d1 = new Date("01/01/2007 12:00:00");
  Date d2 = new Date("01/02/2007 12:00:00");

  //diff between these 2 dates should be 1
  Date d3 = new Date("03/24/2007 12:00:00");
  Date d4 = new Date("03/25/2007 12:00:00");

  Calendar cal1 = Calendar.getInstance();cal1.setTime(d1);
  Calendar cal2 = Calendar.getInstance();cal2.setTime(d2);
  Calendar cal3 = Calendar.getInstance();cal3.setTime(d3);
  Calendar cal4 = Calendar.getInstance();cal4.setTime(d4);

  printOutput("Manual   ", d1, d2, calculateDays(d1, d2));
  printOutput("Calendar ", d1, d2, daysBetween(cal1, cal2));
  System.out.println("---");
  printOutput("Manual   ", d3, d4, calculateDays(d3, d4));
  printOutput("Calendar ", d3, d4, daysBetween(cal3, cal4));
}


private static void printOutput(String type, Date d1, Date d2, long result) {
  System.out.println(type+ "- Days between: " + sdf.format(d1)
                    + " and " + sdf.format(d2) + " is: " + result);
}

/** Manual Method - YIELDS INCORRECT RESULTS - DO NOT USE**/
/* This method is used to find the no of days between the given dates */
public static long calculateDays(Date dateEarly, Date dateLater) {
  return (dateLater.getTime() - dateEarly.getTime()) / (24 * 60 * 60 * 1000);
}

/** Using Calendar - THE CORRECT WAY**/
public static long daysBetween(Date startDate, Date endDate) {
  ...
}

OUTPUT:

Manual - Days between: 01-Jan-2007 and 02-Jan-2007 is: 1

Calendar - Days between: 01-Jan-2007 and 02-Jan-2007 is: 1

---

Manual - Days between: 24-Mar-2007 and 25-Mar-2007 is: 0

Calendar - Days between: 24-Mar-2007 and 25-Mar-2007 is: 1