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: http://support.microsoft.com/?kbid=928388 http://www.microsoft.com/windows/timezone/dst2007.mspx 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? Teo On 2/1/07, Periyasamy, Raj <Raj.Periyasamy@xxxxxxxxxxxx> wrote: Bret, 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. Regards, HTH. Regards, Raj Periyasamy MCSE(Messaging), CCNA ________________________________ From: exchangelist-bounce@xxxxxxxxxxxxx [mailto: exchangelist-bounce@xxxxxxxxxxxxx <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? Thanks Bret Hanson Systems Administrator Yunker Industries, Inc.