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 " +         android.text.format.DateFormat.getDateFormat(this).format(new Date())); 

and I am having another date in format as: 2010-08-25 (i.e. yyyy/mm/dd) ,

so I want to find the difference between date in number of days, how do I find difference in days?

(In other words, I want to find the difference between CURRENT DATE - yyyy/mm/dd formatted date)

Answer 1

Not really a reliable method, better of using JodaTime

  Calendar thatDay = Calendar.getInstance();   thatDay.set(Calendar.DAY_OF_MONTH,25);   thatDay.set(Calendar.MONTH,7); // 0-11 so 1 less   thatDay.set(Calendar.YEAR, 1985);    Calendar today = Calendar.getInstance();    long diff = today.getTimeInMillis() - thatDay.getTimeInMillis(); //result in millis 

Here's an approximation...

long days = diff / (24 * 60 * 60 * 1000); 

To Parse the date from a string, you could use

  String strThatDay = "1985/08/25";   SimpleDateFormat formatter = new SimpleDateFormat("yyyy/MM/dd");   Date d = null;   try {    d = formatter.parse(strThatDay);//catch exception   } catch (ParseException e) {    // TODO Auto-generated catch block    e.printStackTrace();   }      Calendar thatDay = Calendar.getInstance();   thatDay.setTime(d); //rest is the same.... 

Although, since you're sure of the date format... You Could also do Integer.parseInt() on it's Substrings to obtain their numeric values.

Answer 2

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