21 11 / 2013
Have recently discovered that Mongoid support for multi-parameter attributes has been removed in version 4.0. Details can be found in this thread.
Practically it makes it impossible to use <% datetime_select %> helper.
So I have added Classes from Mongoid v.3.x to enable support back in 4.0 with slight amendments to support Rails 4.0.1:
Also make sure that config.autoload_paths is set in application.rb to load lib/* files