Getting the datetime when using Calendar Date Select plugin in an Ajax update operation

Hey,everyone,

I encountered a problem when getting a date through calendar date
select plugin. It’s convenient to put the very
tag(calendar_date_select_tag) in a form, then get the date when the
form is submitted, however, if I don’t put the
calendar_date_select_tag in a form, and just use it as an element
which can show a calendar on the page, now I wanna update a specific
area on the page when my mouse goes over the date on the calendar. so
far, the trouble is I can not fetch the datetime in an onchange event?
My code is as below:

<%= calendar_date_select_tag :e_date, nil, :embedded => true, :year_range => 100, :month_year => "label", :onchange => remote_function(:update=>"events", :url=>study_plan_users_calendars_path) %>
Here comes the message which is updated according to the date

How can I get the datetime which is used as some condition when
updating the specific area?
Or any other idea on solving this updating issue?