[ExchangeList] Re: Exchange 2000 and DST

  • From: "Jason Sherry" <Jason.Sherry@xxxxxxxxxxxx>
  • To: <exchangelist@xxxxxxxxxxxxx>
  • Date: Sat, 3 Feb 2007 09:07:36 -0700

Exchange 5.5 - 2007 stamps messages with the UST\GMT time.  The main
issue is clients that take this time and calculate the time to be
displayed to the clients or in their application.   So if a message
comes in at 8AM MDT Exchange will stamp it as 3PM UST.  When a client
opens the message\item it will look at the time zone setting of the
client to calculate the local time of the message.


The same goes for any items in Exchange, the biggest impact is to
calendar items.  


If I create a meeting for 8AM and I'm in Denver, CO my client will save
it as 3PM UTC [8AM + 7 time zone offset] if the meeting is not during
DST.  When this meeting is sent to other people their clients will
calculate the display time of the meeting based on their time zone and
the UST timestamp of the meeting.  If my client isn't patched and the
meeting is during the new DST periods of 3/11 -4/1 & 12/28 - 11/4 the
meeting will still be saved at 3PM UTC.  If it is patched it will be
saved as 2PM UTC [8AM + 7 time zone offset - 1 DST].  When other clients
open this meeting they get the 2PM UTC time and the clients then adds
the time zone offset to it and adds the DST offset, 2PM UTC + -7 [MST] +
1 DST =  8AM local time in Denver.


So if some clients are patched and others aren't users will have
inconsistent times for the meeting.  This goes for any meeting that is
currently booked during the new DST period that wasn't saved with the
correct time zone offset data.  MS just released the Outlook rebasing
(Time Zone data Update) tool, http://support.microsoft.com/?kbid=931667,
and should be release the server\admin tool soon.  These tools can be
used to reset the UST time for any meeting during the new DST period.
The Outlook tool is a per client tool and the server tool will enable
admins to rebase all items for multiple mailboxes.


OWA and many other applications use CDO to calculate the time for items,
based on their UTC timestamp.  The issue is that CDO has the time zone
data hardcoded in DLLs.  So you must patch those DLLs to have the times
displayed correctly.  If you don't meetings times will be displayed
incorrectly during the new DST period.


The MS suggested patch deployment order is 1st non-Exchange servers ,
then clients, then Exchange servers.   Next you should run the Time Zone
Update tool against all mailboxes. 


You CANNOT manually have client just change their time by an hour since
this will put the client's time out of sync from the DCs.  Kerberos
authentication, which is used by Windows 2000 and higher clients, checks
to make sure the client time, using UTC, is within 5 minutes of the DC
authenticating the client, by default.  If it isn't the client won't be
able to logon. 


Key reading:





From: exchangelist-bounce@xxxxxxxxxxxxx
[mailto:exchangelist-bounce@xxxxxxxxxxxxx] On Behalf Of Teo De Las Heras
Sent: Saturday, February 03, 2007 7:16 AM
To: exchangelist@xxxxxxxxxxxxx
Subject: [ExchangeList] Re: Exchange 2000 and DST


Is this the same case for Exchange 5.5?  Also, won't Exchange stamp the
wrong received time on messages?




On 2/1/07, Periyasamy, Raj <Raj.Periyasamy@xxxxxxxxxxxx> wrote: 


This DST patch specific to Exchange will only matter if you are using
OWA in your environment. If you are using all Outlook clients on
desktops, make sure you rollout the DST patch for the OS on those
clients, as well as the server. Outlook clients use the OS time zone for
calendar and other items, whereas OWA does it differently using CDO. If
you don't have the Exchange 2000 DST patch OWA will show incorrect times
during the 3-4 week period, i.e OWA will assume the old DST standards.



Raj Periyasamy 
MCSE(Messaging), CCNA 



From: exchangelist-bounce@xxxxxxxxxxxxx [mailto:
<mailto:exchangelist-bounce@xxxxxxxxxxxxx> ] On Behalf Of Bret Hanson
Sent: Thursday, February 01, 2007 4:32 PM
To: exchangelist@xxxxxxxxxxxxx
Subject: [ExchangeList] Exchange 2000 and DST


I am being asked by the powers that be at my company what the worst
possible scenario is if we keep our Exchange 2000 server running past
March 11, 2007 without spending the 4 grand for the hot fix. 


While an Exchange 2003 or 2007 upgrade is in our near future, we doubt
it will happen before this date.


At this point, it looks to me like the time stamps on email, calendar
entries, etc will be off by an hour for approx 3-4 weeks until the first
Sunday in April (old DST date) rolls around.  After that point is it
safe to assume email and other Exchange objects would have the correct
time stamp? 


My main fear, is the fear of not knowing what to expect.  Can someone
shed some light or speculate what could happen?




Bret Hanson

Systems Administrator

Yunker Industries, Inc.



Other related posts: