So let me try to understand what you want... if the user enters:
4/3/2009 you would like it to set the date to 4/3/2009, but if they enter 3/30/2009 you would like to use 30/3/2009? is that correct?
What if someone types something that can't be resolved into a date like 21/20/2009? Or are you validating the form in some other way as well? Because of the different date standards, most forms will include a note like: (dd/mm/yyyy), and force people to use the correct format and validate and show an error message if the date is not in the correct format instead of trying to make guesses when the date seems wrong.
We can probably just figure out a simple script to account for the exact scenario you need. There won't be a need to abandon DataAssist because of this simple issue, it is just a matter of fixing the simple issue with what will amount to a few lines of code. No need to scap dozens of pages and hundreds of lines of code.