diff --git a/app/models/rate.rb b/app/models/rate.rb
index a8e766e..425ec46 100644
--- a/app/models/rate.rb
+++ b/app/models/rate.rb
@@ -31,7 +31,14 @@ class Rate < ActiveRecord::Base
     # Check input since it's a "public" API
     raise Rate::InvalidParameterException.new("user must be a User instance") unless user.is_a?(User)
     raise Rate::InvalidParameterException.new("project must be a Project instance") unless project.nil? || project.is_a?(Project)
-
+    raise Rate::InvalidParameterException.new("date must be a valid Date string (e.g. YYYY-MM-DD)") unless date.is_a?(String)
+    
+    begin
+      Date.parse(date)
+    rescue ArgumentError
+      raise Rate::InvalidParameterException.new("date must be a valid Date string (e.g. YYYY-MM-DD)")
+    end
+      
     rate = self.for_user_project_and_date(user, project, date)
     
     return nil if rate.nil?
diff --git a/spec/models/rate_spec.rb b/spec/models/rate_spec.rb
index de22a27..14e0ce3 100644
--- a/spec/models/rate_spec.rb
+++ b/spec/models/rate_spec.rb
@@ -199,7 +199,7 @@ describe Rate, 'for' do
     }.should raise_error(Rate::InvalidParameterException, "user must be a User instance")
   end
   
-  it 'with an invalid project should be nil' do
+  it 'with an invalid project should raise an InvalidParameterException' do
     object = mock('random_object_with_id_attribute')
     Rate.should_not_receive(:for_user_project_and_date)
     lambda {
@@ -207,6 +207,23 @@ describe Rate, 'for' do
     }.should raise_error(Rate::InvalidParameterException, "project must be a Project instance")
   end
   
+  it 'with an invalid object for date should raise an InvalidParameterException' do
+    object = mock('random_object_thats_not_a_string')
+    Rate.should_not_receive(:for_user_project_and_date)
+    lambda {
+      Rate.for(@user, @project, object)
+    }.should raise_error(Rate::InvalidParameterException, "date must be a valid Date string (e.g. YYYY-MM-DD)")
+  end
+
+  it 'with an invalid date string should raise an InvalidParameterException' do
+    Rate.should_not_receive(:for_user_project_and_date)
+    lambda {
+      Rate.for(@user, @project, '2000-13-40')
+    }.should raise_error(Rate::InvalidParameterException, "date must be a valid Date string (e.g. YYYY-MM-DD)")
+  end
+
+
+  
 end
 
 describe Rate, 'for_user_project_and_date (private)' do