How to use values through forms

Basically I need to know how to use forms fields when the name for it
doesn't match a field in my database. I have a form like this.

<td><%= date_select 'assessment', 'ends_at_date', :value => "Click
here..." %>
<%= time_select 'assessment', 'ends_at_time'%></td>

My database has a field called ends_at which is a datetime field that
should have the combination of these 2 forms fields. However, I dont
know how to interact with the values of form fields with ruby in order
to do that. This gives me an error right now because there are no
database fields called ends_at_date or ends_at_time to correspond to.
Does anyone know i can use these two fields and combine them and then
assign that to my ends_at field? Perhaps through the model or
controller. Thank alot :smiley:

is there some reason you don't want to just use datetime_select and
include both in one field?