Error in validating comment edit forms

Hi, and thanks for your work,

When I want to edit a comment I get a validation error about the date field, I have added
this line

if (isset($form['admin']['date'])) {
$form['admin']['date']['#element_validate']=array('calendar_systems_date_validate');
}

after this

function calendar_systems_form_alter(&$form, $form_state, $form_id) {

if (isset($form['author']['date'])) {
$form['author']['date']['#element_validate']=array('calendar_systems_date_validate');
}

and it fixed the issue.