I forgot to set a date of end of poll.
When I call back the poll to modify it, when I click on the end of poll date input box, calendar doesn't appear like it did when I created it. If I type de date manually, it is not saved. And I always got this error message on then list of polls table (column "status") :
Warning: mktime() expects parameter 4 to be long, string given in /homepages/37/d188889042/htdocs/wp-content/plugins/cardoza-wordpress-poll/app/CWPController.class.php on line 295
Thanks for your help.