It appears that sometime in Jan that Google decided to change the format of the pages cached in their system depending on how the cached page was retrieved. For example, consider the page
If you search for the page in Google's index via
and then click on the "Google's cache" link, you will see this page:
But if you try to access the cached version directly via the following URL:
you will see this page:
Notice the font change and the difference in date format ('Jan 21, 2006' --> '21 Jan 2006').
I first noticed the change a few weeks ago. I've also noticed that Google is not always consistent with the heading change. It's possible that the format change is due to changes in different data centers.