Custom date format in a view

Hi...

I created a View and I'd like to customize the Node:Post date field.

I'd like show this field in the following format: dd.mm.yyyy

I typed 'd.m.Y' in the Custom date format text box but I got the following error message:

Validation error, please try again. If this error persists, please contact the site administrator.

Could you please help me?

Thanks for your help.

Pedro