Manual:DateTimeInputWidget
MediaWiki includes a DateTimeInputWidget that can be used for user interfaces that require selecting a date and time. You can see an example of it at Special:ApiSandbox. Click on "action=edit" in the left nav and then scroll down to "basetimestamp".
The code for the widget is located in resources/src/mediawiki.widgets.datetime/.
See also
[edit]- DateInputWidget, which is similar, but only supports dates