title: comparison of Date with ActiveSupport::TimeWithZone failed
body: <p>I have an <code>age</code> method on my <code>Waiver</code> model that looks like:</p>
  
  <pre><code>  def age(date = nil)
  
      if date.nil?
        date = Date.today
      end
      age = 0
      unless date_of_birth.nil?
        age = date.year - date_of_birth.year
        age -= 1 if date &lt; date_of_birth + age.years #for days before birthday
      end
      return age
    end
  </code></pre>
  
  <p>I then have a spec that looks like:</p>
  
  <pre><code>it "calculates the proper age" do
   waiver = FactoryGirl.create(:waiver, date_of_birth: 12.years.ago)
   waiver.age.should == 12
  end
  </code></pre>
  
  <p>When I run this spec I get <code>comparison of Date with ActiveSupport::TimeWithZone failed</code>. What am I doing wrong?</p>
  
  <pre><code>Failures:
  
    1) Waiver calculates the proper age
       Failure/Error: waiver.age.should == 12
       ArgumentError:
         comparison of Date with ActiveSupport::TimeWithZone failed
       # ./app/models/waiver.rb:132:in `&lt;'
       # ./app/models/waiver.rb:132:in `age'
       # ./spec/models/waiver_spec.rb:23:in `block (2 levels) in &lt;top (required)&gt;'
  </code></pre>