Datedropper

Uses the power of datedropper to create an awesome datepicker on your Drupal forms.
http://felicegattuso.com/projects/datedropper/

At the current state the module allows you to set global settings and add the elements you want to target via a settings page.

Works with Form API.

$form['element'] = array(
  '#type' => 'datedropper',
  '#title' => t('Datedropper'),
  '#required' => TRUE,
);

Requirements
elements (http://drupal.org/project/elements)

Later on it will have fully field widget functionality with multiple settings.

Drupal 8

Drupal 8.x version is in the works to.