DanCoulter

Once activated, this plugin will translate every instance of the jQuery UI 
Datepicker plugin on your blog. It even comes with the latest version of 
the jQuery plugin, so that you can add it to pages on your blog.
This will only work with version of the Datepicker plugin that come with 
jQuery UI versions 1.5 or higher.

Datepicker i18n

Globally translate your jQuery UI Datepicker instances.

Robert Wetzlmayr

WordPress uses various methods to convert the original english text strings into the target language. Using the server’s built-in native gettext functions is considerably faster than their PHP equivalent. This plugin checks whether a webserver offers this optional gettext capabilities to WordPress.
<h4>Credits</h4>
German translation by <a href="http://awasteofwords.com/" rel="nofollow ugc">Robert</a>.

Native gettext diagnosis

Diagnose a server's capabilities to use the native gettext extension for translations.

Datepicker i18n vs Native gettext diagnosis