Your day has finally arrived, AT&T One X owners. AT&T just announced that the Android 4.1 Jelly Bean update for its HTC One X will start rolling out today, March 7. The new software will bring with it the usual Jelly Bean goodies, including Google Now and expandable notifications, as well as AT&T-branded apps like AT&T Locker and AT&T DriveMode. One X owners that are hungry for some Jelly Beans can check for the update by connecting to Wi-Fi and going into Settings > About phone > Check for updates.

AT&T originally revealed that its One X would be receiving an update to Jelly Bean back in October 2012. There were no other announcements about the upgrade or when it might begin rolling out after that, though, which makes today's rollout a bit of a surprise. While the update likely took longer to roll out than I'm sure most owners would've liked, it's good to see the AT&T flavor of HTC's former flagship finally joining its One X+ counterpart on Android 4.1.

It's not clear exactly what's packed into this Jelly Bean update because there's no full changelog available it quite yet. However, AT&T has previously said that HTC's Sense 4+ overlay would be coming to the One X, so owners may also be getting a slightly newer flavor of Sense today. Until we hear more, you can find AT&T's abbreviated changelog at the bottom of this post.

UPDATE: As noted by commenter Edgar Brambila, AT&T has taken down the post announcing the update's availability. Stay tuned and we'll share more information as we get it.

UPDATE 2: AT&T has reposted its original blog entry, so it looks like the update should still start rolling out today. These things usually go out in phases, though, so don't fret too much if you don't receive it right away.

• Google Now, which provides you with the latest relevant information you need, when you need it. Whether you’re checking the weather, checking flight information, tracking a package or more, you can get the information that matters most immediately in a single swipe.
• Changes to the notification display that groups updates from the same application together and allows you to expand or collapse any notification.
• The ability to view the full text of an SMS message and the full photo of a MMS in the notification window. 
• An event notifications display that offers more of the event description, allowing you to quickly see relevant details without having to open an app.
• New countdown timer for the front-facing camera.
• This software update will also give you easy access to the following useful apps:
  • AT&T Locker – Allows you to automatically store photos, videos and documents securely in the cloud, so you can access and share from your smartphone or computer.
  • AT&T DriveMode®  - Helps curb texting and driving.  The app can be set-up to automatically send a customizable reply to incoming messages once a vehicle starts moving 25 mph. The auto-reply message is similar to an “out-of-office alert” and can reply to texts, emails and wireless callers letting your friends know that you are driving and unable to respond.*
  • AT&T Messages – Displays all your texts, calls, and voicemail messages together in a single inbox, easily accessible from your computer, tablet, or mobile phone.

Via AT&T Consumer Blog (1), (2)