Stabbed you in the back, since parsing that date will raise an ArgumentError.
Ruby 1.9 switches the slash separated date format to assume day/month/year instead of the previous month/day/year, breaking the parsing for the most common American date format.
Now, I'm not saying that month/day/year is correct, as some other countries use day/month/year.
But for ruby to break your code and not give you an easy way to fix it is troubling.