Precise age calculation..

[Franck Tranchant]

Hi,

After several attempts to calculate the age of someone in Java, i give up and ask for for help !

I would like to display quite a precise age such as :
"Today, you have 10 years, 3 months and 21 days"

I can easilly get the number of Years and the number of Months but i couldnt succeed in getting the exact number of Days...

Any idea for a proper code to display this result ?

[Ilja Preuss]

Can you show us the code you have so far?

[Franck Tranchant]

Of course.
Here is my current code :

import java.text.SimpleDateFormat;
import java.util.Calendar;
import java.util.Locale;
import java.util.Date;
 
StringBuffer returnValue = new StringBuffer("");
 
int     nYear, nMonth, nDay = 0;
String  sYear, sMonth, sDay = "";
 
try
{
   SimpleDateFormat dateFormatter = new SimpleDateFormat("dd/MM/yyyy");
 
   long birthday = dateFormatter.parse("25/04/2004").getTime();
   long today = dateFormatter.parse("24/04/2006").getTime();
 
   Calendar age = Calendar.getInstance(Locale.getDefault());
   age.setTime(new Date(Math.abs(today-birthday)));
 
   nYear  = age.get(Calendar.YEAR)-1970;
   nMonth = age.get(Calendar.MONTH);
   nDay   = age.get(Calendar.DAY_OF_MONTH);
 
   sYear  = (nYear>0?nYear+" year"+(nYear>1?"s":"")+", ":"");
   sMonth = (nMonth>0?nMonth+" month"+(nMonth>1?"s":"")+", ":"");
   sDay   = (nDay>0?nDay+" day"+(nDay>1?"s":""):"");
 
   if ((today-birthday)>0)
   {
      returnValue.append(sYear);
      returnValue.append(sMonth);
      returnValue.append(sDay);

   } else {
 
      returnValue.append("Not born yet !");
   }
 
}
catch(Exception e)
{
   returnValue.append("Exception occured");
}
 
System.out.println(returnValue);

By changing birthday and today values, you'll see that the number of days returned isn't correct...

Any suggestion is welcome.

[Darin Niard]

It seems to work for me. You need to realize that these date classes are not meant to measure duration. That is, you will never see 1 Year, 0 Days, because that does not exist on a calendar. I'm assuming you are seeing 11 months, 31 days, and you think that is wrong, when in fact is not wrong at all. Think about it. 11 months, 31 days is exactly the same as 1 year.

[Franck Tranchant]

Okay for this one.
But in some cases, the result sounds really wrong to me.

For example :
birthday = 25/04/2004
today = 25/06/2004

will return :
2 months, 3 days

I would expect 2 months instead....

[Darin Niard]

It does this because you are storing the difference between dates as a completely different place in time. In your example above:

Mon Mar 02 17:00:00 GMT-07:00 1970
2 months, 2 days

See, when you subtracted the two, they were 30/31 day months you were dealing with. Now, you are storing it as a completely different year, and since Feb only has 28 days, you now get some extra days. Like I said before, storing a duration in a Date/Calendar isn't what you want to do.
[ July 16, 2004: Message edited by: Darin Niard ]

[Franck Tranchant]

Ok I see the problem but cannot find a way to solve it..

I thought this kind of issue was trivial, that's why I posted in the 'Beginner' forum, but maybe it's not...

Anyone has a proposition for a proper way to calculate the exact remaining number of days ?

Many thanx in advance

[Darin Niard]

Well, off the top of my head, you could take the "total days person has been alive" and then expand it out. The only problem is, your highest measurement has to be weeks, because after that, it is no longer constant (months and years vary).

[Michael Dunn]

This needs a lot of testing

import java.util.*;
import java.text.*;
 
class DateDifference
{
  public static void main(String args[])
  {
    SimpleDateFormat sdf = new SimpleDateFormat("yyyy MM dd");
    int dateParts[] = {Calendar.YEAR,Calendar.MONTH,Calendar.DAY_OF_MONTH};
    Calendar today = Calendar.getInstance();
    Calendar birthday = Calendar.getInstance();
    birthday.set(1994,6,21); //months are 0-based
    if(today.before(birthday))
    {
      System.out.println("birthday invalid - date after today, exiting");
      System.exit(0);
    }
    int diff[] = new int[3];
    for(int i = 2; i >= 0; i--)
    {
      while(!sdf.format(birthday.getTime()).split(" ")[i].equals(sdf.format(today.getTime()).split(" ")[i]))
      {
        birthday.add(dateParts[i],1);
        diff[i]++;
      }
    }
    String difference = ""+(diff[0]+" yrs : "+diff[1])+" mths : "+diff[2]+" days";
    System.out.println("Difference = " + difference);
    System.exit(0);
  }
}

[Franck Tranchant]

Thanx Darin and Michael

Michael, I couldn't try your code since I don't have the right version of the JDK, so I did it my way.
It's a little bit longer but I think it works fine.
My purpose was to compare the birthdate of my son with the date of some digital photos and then automaticaly write the right label in an album photo.

Here is my code :

import java.text.ParseException;
import java.text.SimpleDateFormat;
import java.util.Calendar;
import java.util.Date;
 
import org.apache.log4j.Logger;
 
static Logger logger = Logger.getLogger(AgeUtil.class);
 
<..>
 
SimpleDateFormat dateFormat = new SimpleDateFormat("dd/MM/yyyy");
dateFormat.setLenient(false);
 
//-- Results data
StringBuffer returnValue = new StringBuffer("");  
int nbYears, nbMonths, nbDays = 0;
 
try {
  
  //-- Birth data
  String stringDateOfBirth = "26/04/2004";    
  Date dateOfBirth = dateFormat.parse(stringDateOfBirth);
 
  Calendar dayOfBirth = Calendar.getInstance();
  dayOfBirth.clear();
  dayOfBirth.setTime(dateOfBirth);
  int birthDay = 0;
 
  //-- Photo data (will be set dynamically for each photo)
  String stringDateOfPhoto = "25/04/2004";      
  Date dateOfPhoto = dateFormat.parse(stringDateOfPhoto);
  
  Calendar dayOfPhoto = Calendar.getInstance();
  dayOfPhoto.clear();
  dayOfPhoto.setTime(dateOfPhoto);      
  int photoDay = 0;
 
  //-- Basic controls
  if (dayOfPhoto.before(dayOfBirth)){
    throw new Exception("Check out the dateOfPhoto (Date before birthday)");
  } else if (dayOfPhoto.equals(dayOfBirth)) {
    returnValue.append("A few hours");
    return returnValue; 
  }
 
  nbYears = dayOfPhoto.get(Calendar.YEAR) - dayOfBirth.get(Calendar.YEAR);
 
  //-- Number of years calculation
  if (dayOfPhoto.get(Calendar.DAY_OF_YEAR) < dayOfBirth.get(Calendar.DAY_OF_YEAR)) {
    nbYears--;
  } 
  
  //-- Number of months calculation
  if (dayOfPhoto.get(Calendar.DAY_OF_YEAR) < dayOfBirth.get(Calendar.DAY_OF_YEAR)) {
    nbMonths = 12 - ( dayOfBirth.get(Calendar.MONTH) - dayOfPhoto.get(Calendar.MONTH) );
  } else if (dayOfPhoto.get(Calendar.DAY_OF_YEAR) > dayOfBirth.get(Calendar.DAY_OF_YEAR)) {
    nbMonths = dayOfPhoto.get(Calendar.MONTH) - dayOfBirth.get(Calendar.MONTH);
  } else {
    nbMonths=0;
    nbYears++;
  } 
 
  //-- Number of days calculation
  birthDay = dayOfBirth.get(Calendar.DAY_OF_MONTH);
  photoDay = dayOfPhoto.get(Calendar.DAY_OF_MONTH);
 
  if (photoDay < birthDay) {
    
    if (nbMonths > 0) nbMonths--;
    
    //-- Number of days in the preceding month of the photo
    Calendar dayOfPhotoPrecMonth = (Calendar)dayOfPhoto.clone();
    dayOfPhotoPrecMonth.add(Calendar.MONTH, -1);
    int maxNumDaysInMonth = dayOfPhotoPrecMonth.getActualMaximum(Calendar.DAY_OF_MONTH);
 
    nbDays = maxNumDaysInMonth - (birthDay - photoDay);
            
  } else if (photoDay > birthDay) {
    
    nbDays = (photoDay - birthDay);
    
  } else {
    
    nbDays = 0;
  }
 
  //-- Build the result message
  if (nbYears>0){
    returnValue.append(nbYears+ " year" + (nbYears>1?"s":"") );
    if (nbMonths>0) {
      returnValue.append(", ");
    } else if (nbDays>0) {
      returnValue.append(" and ");  
    }
  }
  if (nbMonths>0){
    returnValue.append(nbMonths+ " month" + (nbMonths>1?"s":"") );
    if (nbDays>0) returnValue.append(" and ");    
  }
  if (nbDays>0){
    returnValue.append(nbDays+ " day" + (nbDays>1?"s":"") );          
  }
 
} catch (ParseException pe) {
  logger.error(pe.getClass().toString().substring(6) + " occured");
  logger.error("Message : " + pe.getMessage());
  returnValue.append("Error : Check out the date format");
  
} catch (Exception e) {
  logger.error(e.getClass().toString().substring(6) + " occured");
  logger.error("Message : " + e.getMessage());
  returnValue.append("Error : "+ e.getMessage());
}
 
return returnValue;

Of course, any comment is welcome !
[ July 22, 2004: Message edited by: Franck Tranchant ]

[Michael Dunn]

Michael, I couldn't try your code since I don't have the right version of the JDK

replace the 'while' statement with this (probably a better way to do it, anyway), but still needs testing

while(today.get(dateParts[i]) != birthday.get(dateParts[i]))

[Dirk Schreckmann]

You might like to take a look at the JavaRanch FAQ on Dates.

http://faq.javaranch.com/view?JavaDatesFaq

It includes a section on comparing dates.
[ July 22, 2004: Message edited by: Dirk Schreckmann ]

[Franck Tranchant]

Michael,

I checked your code and it seem to work fine.
The manual incrementation is quite clever and what a code size reduction ! :-)

Thank you all for the assistance.