This is from exercise 13-2 (using dates) in Murach's Java Programming 4. I have the program written but the age comes out incorrect. If you use my birthday Feb 17, 1982 it gives an age of 662. I checked the math by hand and it should give the correct result of 30. If you look at the calculateAge() function I have outputs for each step of the cal…

AgeCalculatorApp

import java.util.*;
import java.text.DateFormat;

public class AgeCalculatorApp
{
    private static Date today = new Date();
    private static GregorianCalendar gregBirthDate = new GregorianCalendar();
    private static Date birthDate = new Date();
    private static DateFormat formattedDate = DateFormat.getDateInstance(DateFormat.SHORT);
    
    public static void main(String[] args)
    {
        //Get the user's birthdate
        System.out.println("Welcome to the age calculator.");
        Scanner sc = new Scanner(System.in);
        int birthMonth = Validator.getInt(sc, "Enter the month you were born (1 to 12): ",
            0, 13) - 1;
        int birthDay = Validator.getInt(sc, "Enter the day of the month you were born: ",
            0, 32);
        int birthYear = Validator.getInt(sc, "Enter the year you were born (four digits): ",
        1874, 2012);
        
        long age = calculateAge(birthMonth, birthDay, birthYear);
        String todaysDate = formattedDate.format(today);
        String formattedBDay = formattedDate.format(birthDate);
        
        System.out.println("Your birth date is: " + formattedBDay);
        System.out.println("Today's date is: " + todaysDate);
        System.out.println("Your age is: " + age);

    }
    
    public static long calculateAge(int birthMonth, int birthDay, int birthYear){
        long age = 0;
        gregBirthDate.set(birthYear, birthMonth, birthDay);
        birthDate = gregBirthDate.getTime();
        long birthDateMS = birthDate.getTime();
        long todayMS = today.getTime();
        long elapsedMS = todayMS - birthDateMS;
        age = elapsedMS / (1000 * 60 * 60 * 24 * 365);
        
        //checking the math one step at a time
        System.out.println(elapsedMS);
        System.out.println(elapsedMS / 1000);
        System.out.println(elapsedMS /(1000 * 60));
        System.out.println(elapsedMS /(1000 * 60 * 60));
        System.out.println(elapsedMS /(1000 * 60 * 60 * 24));
        System.out.println(elapsedMS /(1000 * 60 * 60 * 24 * 365));
        
        return age;
    }
}

Validator

import java.util.Scanner;

public class Validator
{
    public static String getString(Scanner sc, String prompt)
    {
        System.out.print(prompt);
        String s = sc.next();        // read the first string on the line
        sc.nextLine();               // discard any other data entered on the line
        return s;
    }

    public static String getLine(Scanner sc, String prompt)
    {
        System.out.print(prompt);
        String s = sc.nextLine();        // read the whole line
        return s;
    }

    public static int getInt(Scanner sc, String prompt)
    {
        boolean isValid = false;
        int i = 0;
        while (isValid == false)
        {
            System.out.print(prompt);
            if (sc.hasNextInt())
            {
                i = sc.nextInt();
                isValid = true;
            }
            else
            {
                System.out.println("Error! Invalid integer value. Try again.");
            }
            sc.nextLine();  // discard any other data entered on the line
        }
        return i;
    }

    public static int getInt(Scanner sc, String prompt,
    int min, int max)
    {
        int i = 0;
        boolean isValid = false;
        while (isValid == false)
        {
            i = getInt(sc, prompt);
            if (i <= min)
                System.out.println(
                    "Error! Number must be greater than " + min);
            else if (i >= max)
                System.out.println(
                    "Error! Number must be less than " + max);
            else
                isValid = true;
        }
        return i;
    }

    public static double getDouble(Scanner sc, String prompt)
    {
        boolean isValid = false;
        double d = 0;
        while (isValid == false)
        {
            System.out.print(prompt);
            if (sc.hasNextDouble())
            {
                d = sc.nextDouble();
                isValid = true;
            }
            else
            {
                System.out.println("Error! Invalid decimal value. Try again.");
            }
            sc.nextLine();  // discard any other data entered on the line
        }
        return d;
    }

    public static double getDouble(Scanner sc, String prompt,
    double min, double max)
    {
        double d = 0;
        boolean isValid = false;
        while (isValid == false)
        {
            d = getDouble(sc, prompt);
            if (d <= min)
                System.out.println(
                    "Error! Number must be greater than " + min);
            else if (d >= max)
                System.out.println(
                    "Error! Number must be less than " + max);
            else
                isValid = true;
        }
        return d;
    }
}

Here's a three year necrobump for you, probs too late to help with what you were doing.
Here's the line that was messing you up:
AgeCalculatorApp
age = elapsedMS / (1000 * 60 * 60 * 24)/ (365);
Java doesn't like huge multiply strings, so if you collapse all the numbers into one (ie: 86400000), then divide by 365, you'll get the correct output.