This problem actually occurred with peoples who switched over to Android Jelly Bean version 4.2. According to the reports, many people tried to update their December birthday and anniversary dates in the People App but they faced hard luck because the calendar directly skipped from November to January.
Well, it is important for you to note that now, Google has introduced a small 1.1 MB Android 4.2.1 update that is trying to fix this Calendar problem in the people App and prevent 2013 from starting a month early. The Nexus 7 tablet and the Nexus 4 smartphone gadgets has now debuted with version 4.2 of Android Jelly Bean and rolled out to the original Nexus 7 tablet.
The Android 4.2.1 upgrade will roll out this Android glitch from the People App. The people who are signed in to other Android forums might have to wait for some more time. The Android team noticed this problem on a Google+ post. However, Google has now assured the users by promising that this Android malfunction will soon be rolled out so that users can easily update their December birthday dates, anniversaries and other major events on the calendar.