Using virtual attributes for multi-parameter form helpers in Rails

In a Rails application I am working on, I needed to setup a form with a field with a non-standard behaviour. The field represents a date object, so the FormHelper date_select helper looked great; however, the date to display was not the actual date to be set on the database, but the day before. Changing all the data on the DB was a bit risky, so I had to stick with this requirement.
I decided to use a virtual attribute to do this, as it seemed the most elegant solution, so I wrote this in my model:



And this in my controller:



However, trying to send this data to the controller resulted in a "1 error(s) on assignment of multiparameter attributes" error.

The solution I found after some search was this one:



Reference:
http://gabeodess.heroku.com/posts/14