Akshar Soft Solutions

This plugin lets users change their administration language to native English (en_US locale).
This is useful during site development and for people more accustomed to the english administration panel, even if your site 
is in another language. (The frontend will still use the native language.)
This plugin is fully compatible with WooCommerce and can correctly identify and translate frontend / backend AJAX requests. 
If you are using this plugin with Advanced Custom Fields, please move the as-english-wp-admin.php file to the /wp-content/mu-plugins/ folder 
(create it if it does not exist). This is an ACF limitation.
This plugin is developer friendly and small (~200 lines of code). Check the FAQ for customization examples.
Usage
Basic usage
Once you have installed and activated the plugin, navigate to any admin page and check the top admin bar. A button will 
display your current locale. If you click on it, the admin will change to English locale (en_US). To switch back, 
press the button again.
<h3>Requirements</h3>
<ul>
<li>PHP 5.3 or higher</li>
</ul>
<h3>Translations</h3>
<ul>
<li>None</li>
</ul>

AS English Admin

Lets users change their administration language to English

mendezki

Note: This plugin was intended as a quick fix for displaying various english dates in german. It unfortunately does not fully cover all date displays.
Using an english WordPress install and publishing posts in german? Those pesky English dates produced by <code><?php the_time(); ?></code> were getting on my nerves too, hence this plugin. Automagically converts english months and days (except for the initials, so far) to their german equivalent.
Intended usage:
Replacing dates like ‘Thursday, October 22nd’, for instance in your custom built theme or themes that just use the date without ‘posted by..’. Please note: It doesn’t completely ‘deutschify’ your theme’s date representation.
Example: Where some themes would say ‘Posted by Annemarie on Thursday, October 22nd’ only the date part is translated, resulting in ‘Posted by Annemarie on Donnerstag, Oktober 22.’. For complete deutschification one would either, depending on your specific situation:
<ul>
<li>Edit Date Format settings under the Settings > General tab in your WordPress admin area.</li>
<li>Edit your theme’s template files, adapting the <code><?php the_time(); ?></code> template tag appropriately. For a howto on editing the time template tag, check the <a href="https://codex.wordpress.org/Template_Tags/the_time" rel="nofollow ugc">Template Tags/the time Codex page</a>.</li>
<li>Or, as an alternative to this plugin, use a german .po language file.</li>
</ul>
Dutchify in stead of Deutschify?
For the Dutch version of this plugin, visit the <a href="https://wordpress.org/extend/plugins/dutchdate/" rel="ugc">Dutchdate Plugin Page</a>

DeutschDate

Replaces english day and month names with their german equivalent

AS English Admin vs DeutschDate