Omeka has encountered an error

Zend_Date_Exception

unsupported ISO8601 format ()

#0 /var/www/clients/client5/web20/web/application/libraries/Zend/Date.php(1078): Zend_Date->_calculate('set', false, 'c', 'en_US')
#1 /var/www/clients/client5/web20/web/application/libraries/Zend/Date.php(197): Zend_Date->set(false, 'c', 'en_US')
#2 /var/www/clients/client5/web20/web/application/libraries/globals.php(983): Zend_Date->__construct(false, 'c')
#3 /var/www/clients/client5/web20/web/themes/scribe/scripto/index/diff.php(48): format_date(false, 'KKK')
#4 /var/www/clients/client5/web20/web/application/libraries/Omeka/View.php(117): include('/var/www/client...')
#5 /var/www/clients/client5/web20/web/application/libraries/Zend/View/Abstract.php(888): Omeka_View->_run('/var/www/client...')
#6 /var/www/clients/client5/web20/web/application/libraries/Zend/Controller/Action/Helper/ViewRenderer.php(900): Zend_View_Abstract->render('index/diff.php')
#7 /var/www/clients/client5/web20/web/application/libraries/Zend/Controller/Action/Helper/ViewRenderer.php(921): Zend_Controller_Action_Helper_ViewRenderer->renderScript('index/diff.php', NULL)
#8 /var/www/clients/client5/web20/web/application/libraries/Zend/Controller/Action/Helper/ViewRenderer.php(960): Zend_Controller_Action_Helper_ViewRenderer->render()
#9 /var/www/clients/client5/web20/web/application/libraries/Zend/Controller/Action/HelperBroker.php(277): Zend_Controller_Action_Helper_ViewRenderer->postDispatch()
#10 /var/www/clients/client5/web20/web/application/libraries/Zend/Controller/Action.php(527): Zend_Controller_Action_HelperBroker->notifyPostDispatch()
#11 /var/www/clients/client5/web20/web/application/libraries/Zend/Controller/Dispatcher/Standard.php(308): Zend_Controller_Action->dispatch('diffAction')
#12 /var/www/clients/client5/web20/web/application/libraries/Zend/Controller/Front.php(954): Zend_Controller_Dispatcher_Standard->dispatch(Object(Zend_Controller_Request_Http), Object(Zend_Controller_Response_Http))
#13 /var/www/clients/client5/web20/web/application/libraries/Zend/Application/Bootstrap/Bootstrap.php(101): Zend_Controller_Front->dispatch()
#14 /var/www/clients/client5/web20/web/application/libraries/Zend/Application.php(366): Zend_Application_Bootstrap_Bootstrap->run()
#15 /var/www/clients/client5/web20/web/application/libraries/Omeka/Application.php(79): Zend_Application->run()
#16 /var/www/clients/client5/web20/web/index.php(23): Omeka_Application->run()
#17 {main}