urbanAtomic Exception

Exception Type: TypeError
Occurance: /var/www/vhosts/drg.de/httpdocs/site/mod/cp_programm/frontend/overview.php in Line 127

Call Stack :
#0 /var/www/vhosts/drg.de/httpdocs/site/mod/cp_programm/frontend/overview.php(127): mktime()
#1 /var/www/vhosts/drg.de/httpdocs/site/mod/cp_programm/frontend.php(41): require('...')
#2 /var/www/vhosts/drg.de/httpdocs/site/index.php(465): cp_programm_getHTML()
#3 {main}

Error Message: mktime(): Argument #5 ($day) must be of type ?int, string given