Steps to reproduce the issue

Use such code to load a Joomla calendar in a form.
echo JHTML::_('calendar', '', 'filter_start','period_start','%d %B %Y',array('size'=>'10','onchange'=>'document.adminForm.submit();', 'onChange'=>'document.adminForm.submit();'));
When you select a date in the calendar, the form with the name adminForm is submitted.

Expected result

When you use the clear button to clear the date in the calendar the date is cleared in the input field and the onchange event should be called

Actual result

When you use the clear button to clear the date in the calendar the date is cleared in the input field but the onchange event is not called.

System information (as much as possible)

This can be reproduced if you install HikaShop Starter on your website with the orders listing in the backend (menu Components->HikaShop->Orders). We use the Joomla calendar to to filter the orders listing by date ranges.

Additional comments

We were able to fix the issue by adding the code:
self.inputField.onchange();
after the code:
self.inputField.setAttribute('data-alt-value', "0000-00-00 00:00:00"); self.inputField.setAttribute('value', ''); self.inputField.value = '';
in the file media/system/js/fields/calendar.js