I discourage cross-posting, but if you do not frequent the Telematics forum, you may have missed it.
A fix has been created, tested, and is working with an extremely high rate of success for the clock issue that the W221 COMAND units have suffered from for over a year. Your date will sync properly to the GPS time, and the COMAND time will sync with the analog clock. When adjusted for DST on the COMAND, the analog clock will immediately reflect the new time.
Please watch the video so you know what to expect during the process, download the ZIP file in the description, and review the PDF file carefully as it has critical information on how to carry out the update.
I must stress this is not an update that is supported or provided by Daimler AG, MBUSA, LLC, or Harmon Becker, and none of the said entities can be held liable in the event your device is damaged as a result.
Although no damage has been reported, it is done at your risk.
This must be understood before proceeding to download the file and attempt the update.
I am happy to have helped get this to the W221 community free of charge.
It is not something your dealer will likely do since it is not an "official" update, so please do not bother your dealer asking them to apply it. If you are uncomfortable following the instructions, ask a friend who may be more technically comfortable to do it for you. I am interested any all success and failures of this fix. So far, there have been zero reports of devices damaged by the application of this update, and only two instances where it was rejected which I am researching out of very many successful installations.
This update is now officially supported by your local dealer. Mention TIPS document LI82.85-P-069468 and call ahead and schedule an appointment. Also do not forget to ask regarding charges. It may be a free service, or there could a nominal charge.