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Java Gregorian Date

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One of my students asked for an example of how to work with a Gregorian date and timezones in Java. I dug out an old example file from when I taught Java at Regis University.

The code follows:

/*
||  Program name:     MyGregorian.java
||  Created by:       Michael McLaughlin
||  Creation date:    10/07/02
||  History:
|| ----------------------------------------------------------------------
||  Date       Author                   Purpose
||  --------   ----------------------   ---------------------------------
||  dd/mm/yy   {Name}                   {Brief statement of change.}
|| ----------------------------------------------------------------------
||  Execution method: Static class demonstrating timezone setting.
||  Program purpose:  Designed as a stand alone program.
*/
// Class imports.
import java.util.Calendar;
import java.util.GregorianCalendar;
import java.util.TimeZone;
 
// Define MyGregorian class.
public class MyGregorian
{
  // Testing static main() method.
  public static void main(String args[])
  {
    // Set an initial variable.
    String initial = "";
 
    System.out.println("======================================================");
    System.out.println("Value of [user.timezone]: [" + (initial = (null != System.getProperty("user.timezone")) ? "Unset" : System.getProperty("user.timezone")) + "]");
    System.out.println("======================================================");
    GregorianCalendar gc = (GregorianCalendar) Calendar.getInstance();
    System.out.println("Calendar Date:          [" + gc.getTime() + "]");
    gc.add(GregorianCalendar.MONTH,1);
    System.out.println("Calendar Date:          [" + gc.getTime() + "]");
    System.out.println("======================================================");
    System.out.println("Value of [user.timezone]: [" + System.getProperty("user.timezone") + "]");
    System.out.println("Value of [user.timezone]: [" + System.setProperty("user.timezone","") + "]");
 
    gc.add(GregorianCalendar.MONTH,1);
    System.out.println("Calendar Date:          [" + gc.getTime() + "]");
 
    System.out.println("======================================================");
 
    Calendar c = Calendar.getInstance();
    System.out.println("Calendar Date:          [" + c.getTime() + "]");
 
    // Move the date ahead one month, hour and minute.
    c.add(Calendar.MONTH,1);
    System.out.println("Calendar Date:          [" + c.getTime() + "]");
 
    System.out.println("======================================================");
 
  } // End of testing static main() method.
 
} // End of MyGregorian class.

It prints to console:

======================================================
Value of [user.timezone]: [Unset]
======================================================
Calendar Date:          [Thu May 05 23:43:42 MDT 2022]
Calendar Date:          [Sun Jun 05 23:43:42 MDT 2022]
======================================================
Value of [user.timezone]: [America/Denver]
Value of [user.timezone]: [America/Denver]
Calendar Date:          [Tue Jul 05 23:43:42 MDT 2022]
======================================================
Calendar Date:          [Thu May 05 23:43:42 MDT 2022]
Calendar Date:          [Sun Jun 05 23:43:42 MDT 2022]
======================================================

As always, I hope this helps those who need to see and example to work with Gregorian dates.

Written by maclochlainn

May 5th, 2022 at 11:50 pm

Posted in Java,Linux,Unix

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