I can't display the default value of the $date_debut in form. Dpm shows me that the right values are there and I can display $date_debut in #title but not on #default_value. any idea why ?
$timestamp_debut = variable_get('variable_1');
$date_debut = date('d-m-Y',$timestamp_debut);
$form['definition_de_la_période_de_modification']['date_de_debut'] = array(
'#type' => 'date_popup',
'#date_format' => 'd-m-Y',
'#title' => t('Date de début'),
'#default_value' => $date_debut,
'#required' => FALSE,
);
'Y-m-d'
as the date format (and changing$date_debut
to match)