<p>I have a rails form with a datetime_select field. When I try to submit the form, I get the following exception:</p>

<pre><code>ActiveRecord::MultiparameterAssignmentErrors in WidgetsController#update 
1 error(s) on assignment of multiparameter attributes
</code></pre>

<p>If it's a validation error, why don't I see an error on the page?</p>

<p>This is in Rails 2.0.2</p>

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
```
.