Changing label on node edit form
You can easily do this using hook_form_alter(&amp;$form, &amp;$form_state, $form_id) Alter

Hook_form_alter is working before your form shown
Use hook_form_alter in Your site theme template.php file.

Like your theme name is bartik,then use this function their

function bartik_form_alter(&amp;$form, &amp;$form_state, $form_id)
{
//Firstly get form id then use below code

if($form_id=='Your_edit_form_id'){
//here print $form and chek which field label you want to change and then alter that field //like

$form['date'][#label]='Date Field(optional)';
}


}


may this will help you.