In WordPress 4.6 (#29420) localization defaults were added for the jQuery UI datepicker based on the current locale using the new
wp_add_inline_script() function. With 4.6 you can enqueue the datepicker and you are set. It works out of the box.
Instead of using the language files from the jQuery UI project the necessary information, mainly from the
WP_Locale class, is directly passed to the datepicker. The list of localized information:
If you are using the files from jQuery UI in your theme or plugin, please be aware of this change. With 4.6 you can omit calling these files and enqueue the default datepicker which will use the built-in defaults from WordPress.
If you want to change the defaults or add custom settings, you can still use all the arguments from the datepicker. WordPress only sets sane defaults for the chosen locale. But you should check if jQuery UI datepicker is enqueued and you should check if the browser is showing a native datepicker (like Chrome).
@ipstenu has scanned the plugin repo for plugins including the jQuery UI files. The following plugins can be changed to use WordPress’ own translations.
Advanced Booking Calendar, Albo Pretorio On line, Altos Toolbar, AWPCP – Classifieds Plugin, Appointment Calendar, Banner Garden Plugin for WordPress, BBS e-Popup, Beaverlodge Maintenance, Beaverlodge Menu Styler, BigContact Contact Page, Blog Post Calendar Widget, Booking Calendar Contact Form, Events Calendar, Class Booking, Contact Form 7 IE DatePicker and Number Spinner Fix, Custom fields, Datepicker i18n, Easy Calendar, EEXCESS, Event Post Type, Events Made Easy, Events Manager, Social Marketing Scheduler, FormCraft – Form Builder, Date Picker in List Fields for Gravity Forms, Gravity Forms (Spanish), Gravity Forms (nl), inquiry form creator, Jet Event System for BuddyPress, JQuery Accessible Accordion, JQuery Accessible Autocomplete, JQuery Accessible Button, JQuery Accessible Carousel, JQuery Accessible Checkbox, JQuery Accessible Datepicker, JQuery Accessible Dialog, JQuery Accessible Menu, JQuery Accessible Progressbar, JQuery Accessible Slider, JQuery Accessible Tabs, JQuery Accessible Tooltip, JQuery Accessible Tree, Js-appointment, LearnPress – WordPress LMS Plugin, LePress, List Urls, Livemesh SiteOrigin Widgets, Lodgix.com Vacation Rental Listing, Management & Booking Plugin, MailChimp List Subscribe Form, Social Media Share Buttons | MashShare, Member Register, Membership 2, Meta Collections, mind-body, Tribulant Newsletters, Orbis, Order Delivery Date for WooCommerce, OpenWebAnalytics, Pay2Post, PDF Catalog, Pronamic Events, RPB Calendar, Vinum Master Tracking Plugin, Simple Ads Manager, Simple Photos Contest, Sk Multi Tag, Solidres – Hotel booking plugin for WordPress, Cubilis Fastbooker, Surbma – Datepicker localization for Gravity Forms, teachPress, TemplatesNext ToolKit, TheNextTable, Toolset Types, Uiform – Cost Estimation & Payment Form Builder, Uiform – Form Builder, Vacation Rentals, Video Central for WordPress, Visual Form Builder, Webagency Widget – Website builder, WEeventscalendar, WooCommerce Checkout Manager, WooCommerce Quick Donation, WP Agenda, WP-AMD – Global JS and CSS handling, WP Any Form, WP Contact Slider, wp-creator-calculator, WP-CRM – Customer Relations Management for WordPress, WP FEvents Book, wp-greet, WP-Invoice – Web Invoice and Billing, WP Maintenance, WP Online Store, WP-Property – WordPress Powered Real Estate and Property Management, Wp-Recall, WP Scripts Updater, WP Swiper, wpShopGermany Free, and XO Event Calendar.