Consider the following scenario:
You deploy Microsoft Lync Server 2010 Group Chat Server in a Microsoft Lync Server 2010 environment.
You change the time of the Group Chat server to differ from the time of the Group Chat database.
You restart the Channel service on the Group Chat server.
You log on to a Group Chat client.
Note This behavior causes the time of all received messages to be incorrect in the Group Chat client.
You change the time of the Group Chat server to be the same as the Group Chat database.
You log on to the Group Chat client again.
In this scenario, the messages time is still incorrect in the Group Chat client.
This issue occurs because the Channel service caches a time skew value when it starts, and then uses this value during the whole session. This time skew value is added to all the messages that the Group Chat server sends to the Group Chat client.
Note The value of the time skew is based on the time difference between the Group Chat server and the Group Chat database.
To resolve this issue, install the following cumulative update:
2500447 Description of the update for Lync Server 2010 Group Chat: April 2011
To work around this issue, restart the Channel service after you correct the time on the Group Chat server.
Microsoft has confirmed that this is a problem in the Microsoft products that are listed in the "Applies to" section.