Backup Site error

[iboeris]

Hi,
this is my first post.
I've the problem with a procedure to backup the site.
I've install the utilities but when i try do backup all site or one site i received this error.
"String was not recognized as a Valid Date Time"
But i don't understand wich date has a problem.

Escuse me for my bad englis but i am italian

Thx to all
Bye