jQuery UI datepicker deprecated and core usages removed

Introduction

JQueryUI datepicker deprecated due to jQueryUI no longer being supported. The OpenJS Foundation lists jQuery UI as an Emeritus project in https://openjsf.org/projects/ which is described as:

Emeritus projects are those which the maintainers feel have reached or are nearing end-of-life

Browsers Impacted

jQueryUI datepicker was only used as a polyfill for browsers that did not support native datepickers, so most users will not be impacted by this change. After factoring in Drupal's current browser support policy , these are the impacted browsers:

• IE11 (1.74%)
• Safari: (2.3%)
• Opera Mini (1.56%)

Effects

Modules/Themes using jQueryUI datepicker will see a deprecation notice informing them it will no longer be in core when Drupal 9 is released.

For the browsers listed in the previous section, there are no longer datepickers for date fields. Instead, the date must be entered into a text field. For these impacted browsers, additional help text is provided in the placeholder and field description. This includes time, which previously had no instructional text or picker.