SharePoint announced earlier an issue in SharePoint Server service pack 2 that affect the server expiration date and change it to trail 180 days.
Attention: Important Information on Service Pack 2
Microsoft released later on a fix for this issue to be applied after or before installing Service pack 2
Now Office server service pack 2 download has been updated to include the fix directly, so if you have not downloaded service pack 2 yet downloaded the updated and everything will work fine
Updated Service Pack 2 download