Context for "require"

I want to use a utility module (DateUtilities) in a lot of places.

The file, date_utilities.rb, is in \rails_apps\mgdl\lib.

If I want to use it in \rails_apps\mgdl\app\models\compound_event.rb,
how do I qualify it ? I’ve tried “lib\date_utilities”, but I get what I
assume to be a File Not Found error.

So if the module does see the file, then why does my reference to
DateModule::collect_date() report “undefined method `collect_date’ for
DateUtilities:Module” ?

TIA