Multi Model Form Yii Cloning Fields

So hello everyone i need your help ...

i've followed how to create multimodelform with this "multimodelform"

in my first model let's say in "a" i have a field called 'date_created' and in "b" i also have that same field, so i just want to clone that date and also how can i resolve the foreign keys? these two forms has the same foreign key.

thanks