before anyone asked I run the Debug mode and nothing happend.
The problem is that If an invoice is created it is set OK (current date), by the way is that the server date?
If you click on the date field it jumps to the DECEMBER and if not careful it will generate an Invoice with current date but DECEMBER as month. Same happens to the DUE DATE.
I descovered this when a client needed the Generated date 18 of May instead of the December 18.
I cannot edit/change that date manually! cause I end in the spining wheel eror.