The People app in Android 4.2 Jelly Bean does not know of December at the moment, but it will in the near future, it seems.
Following reports coming from users that the application lists only 11 months in the year, Google has acknowledged the issue and announced that it was already looking into the matter.
As you might have learned already, the issue did not offer the option to enter December events in optional fields of the People app, but it did not affect other core applications in Google’s new mobile operating system flavor.
The company has already promised a fix for the flaw, though it did not offer a specific availability date for it.
“Rest assured, this will be fixed soon so that those of you with December birthdays and anniversaries won’t be forgotten by your friends and family,” Google said in a Google+ post.