Since date and time formatting differs regionally, it makes sense to configure them to be language specific. WPML does not do this by default but here’s a way to change that.

Normally you set up the date and time formatting under Settings > General. Since there’s no WPML UI to provide different values per language, we can add a snippet of code that allows you to translate the values using WPML String Translation. First add the following code to your theme’s functions.php:

add_filter( 'option_date_format', function( $format ) {
	do_action( 'wpml_register_single_string', 'Date formats', 'Date format', $format );
	return apply_filters( 'wpml_translate_single_string', $format, 'Date Formats', 'Date format' );
} );
add_filter( 'option_time_format', function( $format ) {
	do_action( 'wpml_register_single_string', 'Date formats', 'Time format', $format );
	return apply_filters( 'wpml_translate_single_string', $format, 'Date Formats', 'Time format' );
} );

Then visit WPML > String Translation and filter by the domain “Date formats”. This should now return 2 rows for the date and time formats where you can enter the alternative values for the non-default languages.

If the Date formats domain does not appear in the dropdown yet, it might be necessary to load a page on your site that displays a date. Then refresh the String Translations page and it should appear in the list.