How to update date field?

If your after a timestamp for when a model is created, just include a
created_at column in your table of DateTime. Rails will
automatically stamp it when it gets created.

Also if your after an update timestamp there is similar functionality from a field updated_at again type DateTime

If you want to convert a text input to a date, you could use

params[:my_date_field].to_time (or to_date)

There is a plugin on www.agilewebdevelopment.com for dates. Maybe you would have some luck with that.

http://www.agilewebdevelopment.com/plugins/flex_times

Or alternatively there is a project called chronic that may be helpful.

Its very early but looks promising

http://rubyforge.org/projects/chronic/

Hope that gets you started…