I have a rails form with a datetime_select field. When I try to submit the form, I get the following exception:
ActiveRecord::MultiparameterAssignmentErrors
It turns out that rails uses something called Multi-parameter assignment to transmit dates and times in small parts that are reassembled when you assign params to the model instance.
My problem was that I was using a datetime_select form field for a date model field. It apparently chokes when the multi-parameter magic tries to set the time on a Date object.
The solution was to use a date_select form field rather than a datetime_select.