I have a custom module where I set two date pop-ups.
$form['set_start_date'] = array(
'#type' => 'date',
'#title' => t('set start date'),
'#required' => TRUE,
);
$form['set_end_date'] = array(
'#type' => 'date',
'#title' => t('set end date'),
'#required' => TRUE,
);
If I select 2017-04-12 as start date, the accepted end date should not be after 2018-04-12.
How can I achieve this?