Google has just started to push Android 4.2.1 (Build JOP40D) update for the Galaxy Nexus and the Nexus 10. You can upgrade your device to Android 4.2.1 via OTA (Over-The-Air) but it might not be available for you right away as it's being rolled out in phases.
The Android 4.2.1 Build JOP40D is a really minor update and is mainly just to fix the “December Bug”, which prevented any date in the month of December from being selected as a birthday, wedding, appointment in the People app. In Short, People App was mising the month “December”, January came next after November. The update also fixes the Bluetooth issues which some of the users were having.
Google has already dropped Android 4.2.1 Build JOP40D into AOSP so if you want you can compile a fresh new AOSP Build for your Galaxy Nexus or Nexus 10 with the new fixes.
Changelog from Android 4.2 JOP40C to Android 4.2.1 JOP40D
Project: platform/build
d4382dd : bump version to 4.2.1
476750c : JOP40D
Project: platform/external/bluetooth/bluedroid
0d15318 : Add HID gamepad/joystick as supported HID devices
Project: platform/frameworks/base
b361b30 : Revert “NumberPicker should adjust min and max when displayed values are set.” (a.k.a. Santa is back)
cc2e849 : Notification vibration improvements: [DO NOT MERGE]
(Source: AndroidCentral)
