Consider the following scenario:
You have a telephone that is running Microsoft Lync 2010 Phone Edition.
Lync 2010 Phone Edition automatically logs in.
You configure the Time Format setting to the 24-hour clock format on the telephone.
You change to another language.
Lync 2010 Phone Edition auto logs in again.
In this scenario, the time format of the telephone is changed to the 12-hour clock format.
Note This issue does not occur when you configure the Time Format setting to 12-hour clock.
To resolve this issue, install the following cumulative update.
For Aastra 6721ip and Aastra 6725ip telephones:
2529978 Description of the cumulative update for Lync 2010 Phone Edition for Aastra 6721ip and Aastra 6725ip: April 2011
For Polycom CX500, Polycom CX600 and Polycom CX3000 telephones:
2529977 Description of the cumulative update for Lync 2010 Phone Edition for Polycom CX500, Polycom CX600 and Polycom CX3000: April 2011
Microsoft has confirmed that this is a problem in the Microsoft products that are listed in the "Applies to" section.