How to get the Bootstrap 3 Datepicker to redirect to an URL when a date is picked?
You can redirect using ajax forms and ctools, first of all you will need to add #ajax property to your form field so the code will be : 

function rbg_date_picker($form, &amp;$form_state) {
  $form['date'] = array(
    '#type' =&gt; 'date_text',
    '#bdtpicker' =&gt; TRUE,
    '#date_format' =&gt; 'Y-m',
    '#datepicker_chain' =&gt; array(
      'my_interval_end[date]' =&gt; 'next',
    ),
    '#datepicker_options' =&gt; array(
      'viewMode' =&gt; 'months',
    ),
    '#ajax' =&gt; array(
      'callback' =&gt; 'SOME_FUNCTION_NAME',
    ),
  );
  return $form;
}


The rest is easy, in callback function you will need to have some code like below :

function SOME_FUNCTION_NAME($form,$form_state) {
  $time = $form_state['values']['date']; // maybe need ['und'][0]['value']
  //Some code to fetch desired values from date like month or year
  ctools_include('ajax');
  ctools_add_js('ajax-responder');
  //Some code to fetch desired values from form and compute 'some-valid-url'.
  $commands[] = ctools_ajax_command_redirect('some-valid-url');
  print ajax_render($commands);
  exit;
}