symfony1 - Symfony change class name for widget used when generating forms -

I have a little question about the Symphony and the automatic creation of the form.

Actually what I want to do is change the square name of the widget that is used when representing a database area of ​​the data type / database.
This is currently creating a sfWidgetFormDateTime () widget, but I would like to generate a widget from a class that I provide, i.e. SfWidgetCustomFormDateTime ()

Anyone got any ideas?

Thanks,

how do you do