Select_date question

Hi all,

I have problem using select_date. I put it in a form and submit the
form. When the page is loaded, user’s selection of the date disappear.

What I want to do is very easy. I want to get the start date and end
date from user ,run the appropriate query and then show the result.
Why does this happen?

my code is like:

Start Date: <%= select_date Date.today%>
End Date: <%= select_date Date.today %>
<%= submit_tag 'Submit',:style=>"height:24px; font-size:12px" %>

Thanks in advance