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having trouble with time zones and daylight savings

Posted on 2011-03-19
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Last Modified: 2013-11-23
So i have this time in my DB
1300550400000
from what i read the display should no if to display daylight or not

when i run this code::
SmsEvents.getStart() returns 1300550400000


        TimeZone pTz = TimeZone.getTimeZone( "PST" );
        DateFormat pdf = DateFormat.getDateTimeInstance( DateFormat.LONG,DateFormat.LONG );
        pdf.setTimeZone( pTz );
        Calendar dayp = Calendar.getInstance();
        dayp.setTimeZone( pTz );
        dayp.setTime( new Date((long)SmsEvents.getStart())  );
        System.out.println( pdf.format( dayp.getTime() ) );

        TimeZone mTz = TimeZone.getTimeZone( "MST" );
        DateFormat mdf = DateFormat.getDateTimeInstance( DateFormat.LONG,DateFormat.LONG );
        mdf.setTimeZone( mTz );
        Calendar daym = Calendar.getInstance();
        daym.setTimeZone( mTz );
        daym.setTime( new Date((long)SmsEvents.getStart())  );
        System.out.println( mdf.format( daym.getTime() ) );

        TimeZone cTz = TimeZone.getTimeZone( "CST" );
        DateFormat cdf = DateFormat.getDateTimeInstance( DateFormat.LONG,DateFormat.LONG );
        cdf.setTimeZone( cTz );
        Calendar dayc = Calendar.getInstance();
        dayc.setTimeZone( cTz );
        dayc.setTime( new Date((long)SmsEvents.getStart())  );
        System.out.println( cdf.format( dayc.getTime() ) );


i get the following results::
March 19, 2011 9:30:00 AM PDT
March 19, 2011 9:30:00 AM MST
March 19, 2011 11:30:00 AM CDT

why is mountain doing this. Am i doing something wrong?
I am confused







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Question by:paries
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18 Comments
 
LVL 47

Expert Comment

by:for_yan
ID: 35172370
What is it that you don't like?
seems logical to me, I guess MST will give the same number as PDT
CDT is two hours difference with PDT
and I guess MDT will be one hour difference with PDT.
Isn't that what you'll expect?
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Author Comment

by:paries
ID: 35172396
so my question is why is it
March 19, 2011 9:30:00 AM MST

should it have not been MDT??

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LVL 47

Expert Comment

by:for_yan
ID: 35172399


I got different output:


March 19, 2011 8:00:00 AM PST
March 19, 2011 9:00:00 AM MST
March 19, 2011 10:00:00 AM CST

Open in new window


I just modified your code a little bit (replacing SMSEvent):

     TimeZone pTz = TimeZone.getTimeZone( "PST" );
            DateFormat pdf = DateFormat.getDateTimeInstance( DateFormat.LONG, DateFormat.LONG );
            pdf.setTimeZone( pTz );
            Calendar dayp = Calendar.getInstance();
            dayp.setTimeZone( pTz );
            dayp.setTime( new Date((long)1300550400000L));
            System.out.println( pdf.format( dayp.getTime() ) );

            TimeZone mTz = TimeZone.getTimeZone( "MST" );
            DateFormat mdf = DateFormat.getDateTimeInstance( DateFormat.LONG,DateFormat.LONG );
            mdf.setTimeZone( mTz );
            Calendar daym = Calendar.getInstance();
            daym.setTimeZone( mTz );
            daym.setTime( new Date((long)1300550400000L)  );
            System.out.println( mdf.format( daym.getTime() ) );

            TimeZone cTz = TimeZone.getTimeZone( "CST" );
            DateFormat cdf = DateFormat.getDateTimeInstance( DateFormat.LONG,DateFormat.LONG );
            cdf.setTimeZone( cTz );
            Calendar dayc = Calendar.getInstance();
            dayc.setTimeZone( cTz );
            dayc.setTime( new Date((long)1300550400000L)  );
            System.out.println( cdf.format( dayc.getTime() ) );

Open in new window


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LVL 47

Expert Comment

by:for_yan
ID: 35172417
When I changed all thre of them to
PDT, MDT nd CDT I got everything in GMT, like that:


March 19, 2011 4:00:00 PM GMT
March 19, 2011 4:00:00 PM GMT
March 19, 2011 4:00:00 PM GMT

Open in new window


Interesting, indeed
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Author Comment

by:paries
ID: 35172434
i am running 1.5 i bet you you are running 1.6
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Expert Comment

by:for_yan
ID: 35172442
I was just posting that I  have Java 1.5 (1.5.0_01)
(even more surprising).
Did you change to that same long number (just to have the codes identical).
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LVL 47

Expert Comment

by:for_yan
ID: 35172449
I'm in Pacific zone, so my local time is 11:06 I guess it is PDT
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Author Comment

by:paries
ID: 35172473
so i am using jdk1.5.0_15
wow this is so confusing....

I am at a loss
thats for you help.
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LVL 47

Expert Comment

by:for_yan
ID: 35172478
It looks like my java does not understand PDT, CDT, MDT;
when I put "ABC" instaed - I also get GMT time in the result
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Author Comment

by:paries
ID: 35172490
yeah that is the same with me.
but if i put in CST it realized i am in daylight savings and shows CDT
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Author Comment

by:paries
ID: 35172509
wow, so i took this very simple jsp and moved to a 1.6.0_20 box

go the same results
March 19, 2011 11:25:22 AM PDT
March 19, 2011 11:25:22 AM MST
March 19, 2011 1:25:22 PM CDT



<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd">

<%@ page import="java.text.SimpleDateFormat" %>
<%@ page import="java.util.*" %>
<%@ page import="java.text.DecimalFormat" %>
<%@ page import="java.text.DateFormat" %>
<%@ page contentType="text/html;charset=UTF-8" language="java" %>

<%
        Date now2 = new Date();

        TimeZone pTz = TimeZone.getTimeZone( "PST" );
        DateFormat pdf = DateFormat.getDateTimeInstance( DateFormat.LONG,DateFormat.LONG );
        pdf.setTimeZone( pTz );
        Calendar dayp = Calendar.getInstance();
        dayp.setTimeZone( pTz );
        dayp.setTime( now2  ) ;
        System.out.println( pdf.format( dayp.getTime() ) );

        TimeZone mTz = TimeZone.getTimeZone( "MST" );
        DateFormat mdf = DateFormat.getDateTimeInstance( DateFormat.LONG,DateFormat.LONG );
        mdf.setTimeZone( mTz );
        Calendar daym = Calendar.getInstance();
        daym.setTimeZone( mTz );
        daym.setTime( now2 );
        System.out.println( mdf.format( daym.getTime() ) );

        TimeZone cTz = TimeZone.getTimeZone( "CST" );
        DateFormat cdf = DateFormat.getDateTimeInstance( DateFormat.LONG,DateFormat.LONG );
        cdf.setTimeZone( cTz );
        Calendar dayc = Calendar.getInstance();
        dayc.setTimeZone( cTz );
        dayc.setTime( now2 );
        System.out.println( cdf.format( dayc.getTime() ) );

%>
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LVL 47

Expert Comment

by:for_yan
ID: 35172511
I'll be in the office this afternoon; I have sveral java's there including 1.6 - I'll give it a try
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LVL 47

Expert Comment

by:for_yan
ID: 35172516
All that looks really strange
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Author Comment

by:paries
ID: 35172533
after some googling seems to be a common problem
if i do TimeZone mTz = TimeZone.getTimeZone( "America/Denver" );
it displays correctly
I think i am going to go that route
thanks for all your help

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Expert Comment

by:for_yan
ID: 35172591
And thanks for this interesting news also
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Accepted Solution

by:
CEHJ earned 2000 total points
ID: 35172614
Yes, 3 letter tzs are deprecated - use the longer city form
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LVL 47

Expert Comment

by:for_yan
ID: 35172753
If all stuff which is deprecated in Java would stop working today - we'll have a disaster much worse than any Japanese tsunami.
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LVL 86

Expert Comment

by:CEHJ
ID: 35172776
Well tzs are a little different than stuff like deprecated methods:

a. they are a moving target for Java
b. they're already either buggy or borderline buggy

For those reasons, it's worth running the tzupdater tool - it won't do you any harm and might do some good
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