joomla back office Failed to parse time string (jerror) at position ....

hello moto;
Pre conditions: Joomla 3.0
i've encountred this error when migrating website from a server to another...
front office worked correctly
back office  no
Try to change $log_path et $tmp_path in configuration.php file
To know the correct directory
create a php file simple.php
<?php
echo getcwd (  );
?>
copy it at the root of the site
invoke it from web browser
get your directory
copy it an d and add /logs for logs and tmp for tmp dir