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Date conversion

HOSROW
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Last Modified: 2010-03-31
How can I convert the result of java.util.Date() to CST(CentralStandardTime) considering daylight savings.
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Commented:
How can I convert the result of java.util.Date() to CST(CentralStandardTime) considering daylight savings.
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Commented:
are you want this?

import java.util.Date;
import java.text.*;

public class TTestDate
{
      public static void main(String[] args)
      {
            SimpleDateFormat bartDateFormat =
            new SimpleDateFormat(""yyyy-MM-dd-EEEE hh:mm:ss);

            Date date = new Date();

            System.out.println(bartDateFormat.format(date));
      }
}
Mick BarryJava Developer
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Top Expert 2010

Commented:
The Date class does not store any timezone information.
Here's an example:

 // get the supported ids for GMT-08:00 (Pacific Standard Time)
 String[] ids = TimeZone.getAvailableIDs(-8 * 60 * 60 * 1000);
 // if no ids were returned, something is wrong. get out.
 if (ids.length == 0)
     System.exit(0);

 // create a Pacific Standard Time time zone
 SimpleTimeZone pdt = new SimpleTimeZone(-8 * 60 * 60 * 1000, ids[0]);

// get the supported ids for GMT-06:00 (Central Standard Time)
 ids = TimeZone.getAvailableIDs(-6 * 60 * 60 * 1000);

 // create a Central Standard Time time zone
 SimpleTimeZone cdt = new SimpleTimeZone(-6 * 60 * 60 * 1000, ids[0]);

 // set up rules for daylight savings time
 pdt.setStartRule(Calendar.APRIL, 1, Calendar.SUNDAY, 2 * 60 * 60 * 1000);
 pdt.setEndRule(Calendar.OCTOBER, -1, Calendar.SUNDAY, 2 * 60 * 60 * 1000);

 // create a GregorianCalendar with the Pacific Daylight time zone
 // and the current date and time
 Calendar calendar = new GregorianCalendar(pdt);

Date myDateInMyTimeZone = new Date();
 calendar.setTime(myDateInMyTimeZone);

 // print out a bunch of interesting things
 System.out.println("ERA: " + calendar.get(Calendar.ERA));
 System.out.println("YEAR: " + calendar.get(Calendar.YEAR));
 System.out.println("MONTH: " + calendar.get(Calendar.MONTH));
 System.out.println("WEEK_OF_YEAR: " + calendar.get(Calendar.WEEK_OF_YEAR));
 System.out.println("WEEK_OF_MONTH: " + calendar.get(Calendar.WEEK_OF_MONTH));
 System.out.println("DATE: " + calendar.get(Calendar.DATE));
 System.out.println("DAY_OF_MONTH: " + calendar.get(Calendar.DAY_OF_MONTH));
 System.out.println("DAY_OF_YEAR: " + calendar.get(Calendar.DAY_OF_YEAR));
 System.out.println("DAY_OF_WEEK: " + calendar.get(Calendar.DAY_OF_WEEK));
 System.out.println("DAY_OF_WEEK_IN_MONTH: "
                    + calendar.get(Calendar.DAY_OF_WEEK_IN_MONTH));
 System.out.println("AM_PM: " + calendar.get(Calendar.AM_PM));
 System.out.println("HOUR: " + calendar.get(Calendar.HOUR));
 System.out.println("HOUR_OF_DAY: " + calendar.get(Calendar.HOUR_OF_DAY));
 System.out.println("MINUTE: " + calendar.get(Calendar.MINUTE));
 System.out.println("SECOND: " + calendar.get(Calendar.SECOND));
 System.out.println("MILLISECOND: " + calendar.get(Calendar.MILLISECOND));
 System.out.println("ZONE_OFFSET: "
                    + (calendar.get(Calendar.ZONE_OFFSET)/(60*60*1000)));
 System.out.println("DST_OFFSET: "
                    + (calendar.get(Calendar.DST_OFFSET)/(60*60*1000)));

calendar.setTimeZone(cdt);

// print out a bunch of interesting things
 System.out.println("ERA: " + calendar.get(Calendar.ERA));
 System.out.println("YEAR: " + calendar.get(Calendar.YEAR));
 System.out.println("MONTH: " + calendar.get(Calendar.MONTH));
 System.out.println("WEEK_OF_YEAR: " + calendar.get(Calendar.WEEK_OF_YEAR));
 System.out.println("WEEK_OF_MONTH: " + calendar.get(Calendar.WEEK_OF_MONTH));
 System.out.println("DATE: " + calendar.get(Calendar.DATE));
 System.out.println("DAY_OF_MONTH: " + calendar.get(Calendar.DAY_OF_MONTH));
 System.out.println("DAY_OF_YEAR: " + calendar.get(Calendar.DAY_OF_YEAR));
 System.out.println("DAY_OF_WEEK: " + calendar.get(Calendar.DAY_OF_WEEK));
 System.out.println("DAY_OF_WEEK_IN_MONTH: "
                    + calendar.get(Calendar.DAY_OF_WEEK_IN_MONTH));
 System.out.println("AM_PM: " + calendar.get(Calendar.AM_PM));
 System.out.println("HOUR: " + calendar.get(Calendar.HOUR));
 System.out.println("HOUR_OF_DAY: " + calendar.get(Calendar.HOUR_OF_DAY));
 System.out.println("MINUTE: " + calendar.get(Calendar.MINUTE));
 System.out.println("SECOND: " + calendar.get(Calendar.SECOND));
 System.out.println("MILLISECOND: " + calendar.get(Calendar.MILLISECOND));
 System.out.println("ZONE_OFFSET: "
                    + (calendar.get(Calendar.ZONE_OFFSET)/(60*60*1000)));
 System.out.println("DST_OFFSET: "
                    + (calendar.get(Calendar.DST_OFFSET)/(60*60*1000)));

Presto!
Oh, btw, the code above is adapted from the Javadocs in java.util.Calendar
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Top Expert 2016

Commented:
           SimpleDateFormat sdf = new SimpleDateFormat("dd-MM-yyyy zzz");
            sdf.setTimeZone(TimeZone.getTimeZone("CST"));
            System.out.println(sdf.format(new Date()));
Mick BarryJava Developer
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Top Expert 2010

Commented:
>  SimpleDateFormat sdf = new SimpleDateFormat("dd-MM-yyyy zzz");
>   sdf.setTimeZone(TimeZone.getTimeZone("CST"));
>     System.out.println(sdf.format(new Date()));

That just displays it, it doesn't actually convert anything.

You need to use the Calendar class as already mentioned.
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Top Expert 2016

Commented:
SimpleDateFormat already has an internal Calendar
Mick BarryJava Developer
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Top Expert 2010

Commented:
So??? It's not for doing conversions, nor can it be used for that purpose.
And even if it could it seems silly to create a SDF just to use it's 'internal' Calendar.
orangehead911's code will show you how to do conversion.
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Top Expert 2016

Commented:
>>It's not for doing conversions

Are you sure? ;-)

>>And even if it could it seems silly to create a SDF just to use it's 'internal' Calendar.

Why? - since

a. you've probably got to format it anyway at some point
b. it's more likely to be error free if you let Sun do it
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Top Expert 2016

Commented:
>>Accept: orangehead911 {http:#10673053}

Why so? - there's no need to use anything other than a DateFormat since it's almost certain that a DateFormat will be needed anyway
Mick BarryJava Developer
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Top Expert 2010

Commented:
The question doesn't ask about formatting the date, the Calendar class is used for timezone conversions. DateFormat is not required.
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Top Expert 2016

Commented:
As explained already the DateFormat class is almost certainly going to be needed. It already contains a Calendar
Mick BarryJava Developer
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Top Expert 2010

Commented:
> . It already contains a Calendar

But its a lot easier and more flexible to just create your own Calendar providing you with full access to it's functionality. The internal Calendar in DateFormat is not intended for being used to do custom timezone conversions.
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Top Expert 2016

Commented:
TimeZone conversion is actually one of the most important functions of the contained Calendar. You don't need to mess around with your own Calendar

sdf.setTimeZone(TimeZone.getTimeZone("CST"));
sdf.format(date);

will fulfil the requirement
Mick BarryJava Developer
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Top Expert 2010

Commented:
The code posted by orangehead911 provides a far more flexible and efficient solution
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Top Expert 2016

Commented:
LOL
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Top Expert 2016

Commented:
As mentioned earlier - a Calendar is unnecessary for converting between time zones
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Top Expert 2016

Commented:
ok ;-)
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