undefined method `calendar_date_select_tag'


I am trying to use the 'Calendar Date Select' plugin

I've copied all the necessary files (javascript + css +
calendar_date_select.rb and so forth files). Further, I added <%=
calendar_date_select_includes "blue" %> line of code in my
layouts/application.rhtml and finally restarted my Apache server.

But I keep on getting:
undefined method `calendar_date_select_tag'
when I try and use this method in my View.

Any ideas so as to what I might be missing? Any help greatly
appreciated. Thanks.