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Working Java code example for date/time you see below, but first some remarks about some important thing: your code will not work properly if your computer time or timezone is set wrong. You can use timezone updater tool from SUN.

Timezone Updater Tool: the TZUpdater tool is provided to allow you to update installed Java Development Kit (JDK) and Java Runtime Environment (JRE) software with more recent timezone data, to accommodate daylight saving time (DST) changes in different countries.Sun recommends that you use the latest Sun Java SE platform JDK or JRE update release as the preferred means of delivering both timezone data updates and other product improvements, such as security fixes. To see which JDK or JRE update release incorporates the updated timezone data for your locale, see Timezone Data Versions in the JRE Software. However, if you are unable to use Sun's latest JDK or JRE update release, the TZUpdater tool provides a means of updating timezone data while leaving other system configuration and dependencies unchanged.

If you looking at extensive implementation time/date functionality in Java I recommend you to look at Gannt Project Tool. It has source code at the site which you can use as an example of extensive usage day/ time Java functionality in running java tools.

Code:



 

 // -----------------------------------------------------------------------------

// DateExample.java

// -----------------------------------------------------------------------------



/*

 * =============================================================================

 * Copyright (c) 1998-2005 Jeffrey M. Hunter. All rights reserved.

 * 

 * All source code and material located at the Internet address of

 * http://www.idevelopment.info is the copyright of Jeffrey M. Hunter, 2005 and

 * is protected under copyright laws of the United States. This source code may

 * not be hosted on any other site without my express, prior, written

 * permission. Application to host any of the material elsewhere can be made by

 * contacting me at jhunter@idevelopment.info.

 *

 * I have made every effort and taken great care in making sure that the source

 * code and other content included on my web site is technically accurate, but I

 * disclaim any and all responsibility for any loss, damage or destruction of

 * data or any other property which may arise from relying on it. I will in no

 * case be liable for any monetary damages arising from such loss, damage or

 * destruction.

 * 

 * As with any code, ensure to test this code in a development environment 

 * before attempting to run it in production.

 * =============================================================================

 */



import java.util.Date;

import java.text.ParseException;

import java.text.SimpleDateFormat;



/**

 * -----------------------------------------------------------------------------

 * Used to provide an example that exercises most of the functionality of the 

 * java.util.Date class.  A Date object represents a precise moment in time, 

 * down to the millisecond. Dates are represented as a long that counts the 

 * number of milliseconds since midnight, January 1, 1970, Greenwich Meantime.

 * 

 * @version 1.0

 * @author  Jeffrey M. Hunter  (jhunter@idevelopment.info)

 * @author  http://www.idevelopment.info

 * -----------------------------------------------------------------------------

 */



public class DateExample {



    /**

     * Helper utility used to print

     * a String to STDOUT.

     * @param s String that will be printed to STDOUT.

     */

    private static void prt(String s) {

        System.out.println(s);

    }



    private static void prt() {

        System.out.println();

    }



    private static void doDateExample() {



        // To create a Date object for the current 

        // date and time use the noargs Date() constructor like this:



        prt("CURRENT DATE/TIME");

        prt("=======================================================");

        Date now = new Date();

        prt("  new Date()                   : " + now);

        prt();





        // To create a Date object for a specific time, pass the number of 

        // milliseconds since midnight, January 1, 1970, Greenwich Meantime 

        // to the constructor, like this:

        //

        // Establish a date object set in milliseconds

        // relative to 1/1/1970 GMT



        prt("DATE OBJECT FOR SPECIFIC TIME");

        prt("=======================================================");

        Date specificDate1 = new Date(24L*60L*60L*1000L);

        Date specificDate2 = new Date(0L);

        prt("  new Date(24L*60L*60L*1000L) : " + specificDate1);

        prt("  new Date(0L)                : " + specificDate2);

        prt();





        // You can return the number of milliseconds in the Date 

        // as a long, using the getTime() method. For example, 

        // to time a block of code, you might do this

        prt("USE getTime() TO RETURN MILLISECONDS");

        prt("=======================================================");

        Date startTime = new Date();

        prt("  Start Time : " + startTime);

        // ....

        // Insert ant "timed code" here...

        // ...

        System.out.print("  ");

        for (int i = 0; i < 10000000; i++) {

            if ((i % 1000000) == 0) {

                System.out.print(".");

            }

            // More "timed" code

        }

        prt();

        Date endTime = new Date();

        prt("  End Time  : " + endTime);

        long elapsed_time = endTime.getTime() - startTime.getTime();

        prt("That took " + elapsed_time + " milliseconds");

        prt();





        // You can change a Date by passing the new date as a number of 

        // milliseconds since midnight, January 1, 1970, GMT, to the setTime() 

        // method, like this: 

        prt("USE gsetTime() TO CHANGE A DATE OBJECT");

        prt("=======================================================");

        Date changeDate = new Date();

        prt("  new Date()                 : " + changeDate);

        changeDate.setTime(24L*60L*60L*1000L);

        prt("  setTime(24L*60L*60L*1000L) : " + changeDate);

        prt();





        // The before() method returns true if this Date is before the Date 

        // argument, false if it's not.

        // For example 

        //   if (midnight_jan2_1970.before(new Date())) {

        // The after() method returns true if this Date is after the Date 

        // argument, false if it's not.

        // For example 

        //   if (midnight_jan2_1970.after(new Date())) {

        // The Date class also has the usual hashCode(), 

        // equals(), and toString() methods.

        prt("COMPARE DATES USING: before(), after(), equals()");

        prt("=======================================================");



        Date compareDateNow1  = new Date();

        Date compareDateNow2  = (Date) compareDateNow1.clone();

        Date compareDate1970  = new Date(24L*60L*60L*1000L);



        prt("  Compare (Equals):");

        prt("    - " + compareDateNow1);

        prt("    - " + compareDateNow2);

        if (compareDateNow1.equals(compareDateNow2)) {

            prt("    - The two dates are equal.");

        } else {

            prt("    - The two dates are NOT equal.");

        }

        prt();



        prt("  Compare (Equals):");

        prt("    - " + compareDateNow1);

        prt("    - " + compareDate1970);

        if (compareDateNow1.equals(compareDate1970)) {

            prt("    - The two dates are equal.");

        } else {

            prt("    - The two dates are NOT equal.");

        }

        prt();



        prt("  Compare (Before):");

        prt("    - " + compareDateNow1);

        prt("    - " + compareDate1970);

        if (compareDateNow1.before(compareDate1970)) {

            prt("    - " + compareDateNow1 + " comes before " + compareDate1970 + ".");

        } else {

            prt("    - " + compareDateNow1 + " DOES NOT come before " + compareDate1970 + ".");

        }

        prt();



        prt("  Compare (After):");

        prt("    - " + compareDateNow1);

        prt("    - " + compareDate1970);

        if (compareDateNow1.after(compareDate1970)) {

            prt("    - " + compareDateNow1 + " comes after " + compareDate1970 + ".");

        } else {

            prt("    - " + compareDateNow1 + " DOES NOT come after " + compareDate1970 + ".");

        }

        prt();







        prt("RETRIEVE MILLISECONDS");

        prt("=======================================================");



        // Establish a date object set in milliseconds relative to 1/1/1970 GMT

        Date y = new Date(1000L*60*60*24);



        // Retrieve the number of milliseconds since 1/1/1970 GMT (31536000000)

        long n = y.getTime();

        prt("  Number of milliseconds since 1/1/1970 (GMT) : " + n);



        // Computes a hashcode for the date object (1471228935)

        int i = y.hashCode();

        prt("  Hash code for object                        : " + i);



        // Retrieve the string representation of the date (Thu Dec 31 16:00:00 PST 1970)

        String s = y.toString();

        prt("  String  representation of date              : " + s);

        prt();



        prt("PARSE STRING TO DATE");

        prt("=================================================================");

        Date   newDate;

        String inputDate = "1994-02-14";

        SimpleDateFormat formatter = new SimpleDateFormat("yyyy-MM-dd");

        System.out.print("  " + inputDate + " parses as ");

        try {

            newDate = formatter.parse(inputDate);

            prt(newDate + ".");

        } catch (ParseException e) {

            prt("Unparseable using " + formatter + ".");

        }    

        prt();



    }





    public static void main(String[] args) {

        prt();

        doDateExample();

    }



}