Currently you have Start/Slut fields defined as

Look at data/CRMEntity.php function "insertIntoEntityTable"

There we can see call getValidDBInsertDateFormat located at include/utils/utils.php

if we input "18-08-2016" then on line 1793 $insert_value will become "2016-08-17", that is ok

But in case of date with time "13-07-2018 00:00:00"

$insert_value will become "2018 00:00:00-07-13", and this can not be properly parsed, and on line 1799 will returns empty string