I have checked the executed command and the returned value follows the ISO format.
The debug log says the following:
21:19:14.781 [DEBUG] [.o.b.exec.internal.ExecBinding:177 ] - transformed response is '2016-04-15T17:00:20'
21:19:14.807 [DEBUG] [ore.internal.items.ItemUpdater:73 ] - Received update of a not accepted type (StringType) for item Consumo_date
I don’t see anything on the wiki page but it is possible the Exec binding doesn’t know how to populate a DateTime Item. You can try using a String and a rule to populate the DateTime type.