Upgraded version of Year Field for ACF 4.x

Here is an upgraded version of Will Ashworth "Advanced Custom Fields (ACF) - Year Field add-on" [ https://github.com/ashworthconsulting/acf-year-field ] based on the ‘my_field’ template file [ check http://www.advancedcustomfields.com/resources/tutorials/creating-a-new-field-type/ for more infos ].

It is not a plugin so in order to make it work it has to be copied in a "fields" folder inside the template folder and then this code needs to be added to the functions.php:
add_action('acf/register_fields', 'my_register_fields');

function my_register_fields()
{
	include_once('fields/years-v4.php');
}