has_many :through questions

Where's the :through from the subject line?

Anyway, this should work:

Hour.find(:first, :conditions=>['weeks.month_id=?',month_id], :include=>:week)

This instructs AR to add a join to the table from the hours table to
the weeks table. AR then makes the table available as 'weeks' for use
in the condition.

Cheers,
Max