> ## Documentation Index
> Fetch the complete documentation index at: https://doc.lucidworks.com/llms.txt
> Use this file to discover all available pages before exploring further.

# Appkit SDK 4.2.1 Release Notes

[localhost link]: http://localhost:3000/docs/4/app-studio/release-notes/appkit/4.2.1-release-notes

[mintlify link]: https://doc.lucidworks.com/docs/4/app-studio/release-notes/appkit/4.2.1-release-notes

[old doc.lw link]: https://doc.lucidworks.com/app-studio/4.2/980

**Release date:** 8 March 2019

## Upgrading to this version

In apps created with prior versions of Fusion App Studio, you can **Upgrade Appkit in Existing Apps**.

<Accordion title="Upgrade Appkit in Existing Apps">
  When you create an Appkit webapp, it uses a specific version of Appkit. Appkit releases occur independently of App Studio releases.

  You can upgrade web apps to use the latest version of Appkit.

  **How to upgrade**

  1. Stop the app.
  2. In the `package.json` file at the root of your project, update the `appkit-ui` dependency to the latest Appkit version, for example:

     ```json theme={"dark"}
     "appkit-ui": "http://appkit.lucidworks.com/repo/4.2.0/appkit-ui.tar.gz",
     ```
  3. In the `pom.xml` file at the root of your project, update the value of the `parent.version` property to the latest Appkit version, for example:

     ```xml theme={"dark"}
         <parent>
             <groupId>twigkit</groupId>
             <artifactId>twigkit.app.js</artifactId>
             <version>4.2.0</version>
         </parent>
     ```
  4. Upgrade the Appkit Social module, if required.
  5. Perform any additional upgrade steps that are required for a specific Appkit upgrade. See the [Appkit Release Notes](/docs/4/app-studio/release-notes/appkit/overview) for more information.
  6. Start the app.
</Accordion>

## New features and improvements

There are no new features or improvements in this release.

## Fixed issues

The following issue is fixed in this release:

* Using a two-date time picker widget, a user could select a From time that was after the To time. The `widget:date-range` element now ensures that the user can only select a From time that precedes the To time.