After you install the August 2011 cumulative time zone update for Windows operating systems in a Microsoft Exchange Server 2010 environment, some time zone information in Outlook Web App (OWA) is not synchronized with the installed Windows operating system. For example, some names of the existing time zones are incorrect, or some names of new time zones are displayed in English only.
Additionally, some time zones are displayed incorrectly in the Current Time Zone list. For example, OWA displays (UTC +03:00) Tbilisi. However, Tbilisi uses the (UTC +04:00) Tbilisi time zone.
Note The time zone information that is not synchronized is located in Regional Settings in OWA.
This issue occurs because OWA reads the time zone information from a file that is not synchronized with the latest daylight saving time (DST) in the Windows registry.
To resolve this issue, install Update Rollup 6 for Exchange Server 2010 Service Pack 1. For more information, click the following article number to view the article in the Microsoft Knowledge Base:
2608646 Description of Update Rollup 6 for Exchange Server 2010 Service Pack 1
Microsoft has confirmed that this is a problem in the Microsoft products that are listed in the "Applies to" section.
For more information about the latest time zone update for Windows operating systems, click the following article number to view the article in the Microsoft Knowledge Base:
2570791 August 2011 cumulative time zone update for Windows operating systems