Week numbers in the Outlook Web App and Outlook calendars are mismatched in an Exchange Server 2010 environment

In a Microsoft Exchange Server 2010 environment, the week numbers that are displayed in the Outlook Web App calendar do not match the week numbers that are displayed in the Microsoft Outlook calendar. For example, in the English version of Outlook Web App, the first week in 2013 is numbered "2." However, in the English version of Microsoft Outlook 2010, the first week in 2013 is numbered "1."

Notes

• To display the week number in Outlook Web App, select the Show week numbers in Month View check box in the Calendar settings.
• To display the week number in Outlook 2010, select the Show week numbers in the month view and in the Date Navigator check box. This check box is located under the Display options heading in the Calendar tab of the Outlook Options dialog box.

This issue occurs because Outlook Web App uses a different mechanism to calculate week numbers.

To resolve this issue, install the following update rollup: Note After you apply this update rollup, you can run the Get-MailboxCalendarConfiguration cmdlet together with the FirstWeekOfYear parameter to display the first week of the year. Additionally, you can run the Set-MailboxCalendarConfiguration cmdlet together with the FirstWeekOfYear parameter to set the first week of the year based on one of the following values:

• FirstDay
• FirstFourDayWeek
• FirstFullWeek

Microsoft has confirmed that this is a problem in the Microsoft products that are listed in the "Applies to" section.

For more information about a similar issue that occurs in an Exchange Server 2007 environment, click the following article number to view the articles in the Microsoft Knowledge Base: For more information about the Get-MailboxCalendarConfiguration cmdlet, go to the following Microsoft website:For more information about the Set-MailboxCalendarConfiguration cmdlet, go to the following Microsoft website:For more information about the CalendarWeekRule enumeration, go to the following Microsoft website: