diff --git a/app/models/cost_entry.rb b/app/models/cost_entry.rb
index c2e14388d3..baed0ddb73 100644
--- a/app/models/cost_entry.rb
+++ b/app/models/cost_entry.rb
@@ -30,9 +30,15 @@ class CostEntry < ActiveRecord::Base
     errors.add :issue_id, :activerecord_error_invalid if (issue_id && !issue) || (issue && project!=issue.project)
     
     errors.add :user_id, :activerecord_error_invalid unless (user == User.current) || (User.current.allowed_to? :book_costs, project)
+    begin
+      spent_on.to_date
+    rescue Exception
+      errors.add :spent_on, :activerecord_error_invalid
+    end
   end
   
   def before_save
+    self.spent_on &&= spent_on.to_date
     update_costs
     issue.save
   end
diff --git a/app/models/rate.rb b/app/models/rate.rb
index 964a4ad511..1fddbd74af 100644
--- a/app/models/rate.rb
+++ b/app/models/rate.rb
@@ -1,5 +1,6 @@
 class Rate < ActiveRecord::Base
   validates_numericality_of :rate, :allow_nil => false, :message => :activerecord_error_invalid
+  validates_format_of :valid_from, :with => /^\d{4}-\d{2}-\d{2}/
 
   def self.clean_currency(value)
     if value && value.is_a?(String)
@@ -10,4 +11,15 @@ class Rate < ActiveRecord::Base
       value
     end
   end
+  
+  def validate
+    valid_from.to_date
+  rescue Exception
+    errors.add :valid_from, :activerecord_error_invalid
+  end
+
+  def before_save
+    self.valid_from &&= valid_from.to_date
+  end
+
 end
\ No newline at end of file
diff --git a/spec/models/cost_entry_spec.rb b/spec/models/cost_entry_spec.rb
index e7c55e9c49..a6dfbb6716 100644
--- a/spec/models/cost_entry_spec.rb
+++ b/spec/models/cost_entry_spec.rb
@@ -44,6 +44,18 @@ describe CostEntry do
     @example.rate.should_not == rates("cheap_one")
     @example.costs.should == cheap.rate
   end
+  
+  it "should update cost if a new rate is added in between" do
+    @example.cost_type = cost_types("umbrella")
+    @example.spent_on = 3.days.ago
+    @example.units = 1
+    @example.save!
+    @example.costs.should == rates("cheap_three").rate
+    cheap = CostRate.create! :valid_from => 3.days.ago.to_date, :rate => 1.0, :cost_type => cost_types("umbrella")
+    @example.reload
+    @example.rate.should_not == rates("cheap_three")
+    @example.costs.should == cheap.rate
+  end
 
   it "should update cost if a spent_on changes" do
     @example.units = 1