diff --git a/app/models/contract.rb b/app/models/contract.rb
index 6275192..57e0e26 100644
--- a/app/models/contract.rb
+++ b/app/models/contract.rb
@@ -13,6 +13,7 @@ class Contract < ActiveRecord::Base
   validates_presence_of :end_date
   validates_presence_of :executed
   validates_inclusion_of :discount_type, :in => %w($ %), :allow_blank => true, :allow_nil => true
+  validate :start_and_end_date_are_valid
 
   # Accessors
   attr_accessible :name
@@ -28,4 +29,9 @@ class Contract < ActiveRecord::Base
   attr_accessible :po_number
   attr_accessible :details
 
+  def start_and_end_date_are_valid
+    if start_date && end_date && end_date < start_date
+      errors.add :end_date, :greater_than_start_date
+    end
+  end
 end
diff --git a/test/unit/contract_test.rb b/test/unit/contract_test.rb
index 8532fe7..df9efcf 100644
--- a/test/unit/contract_test.rb
+++ b/test/unit/contract_test.rb
@@ -16,8 +16,13 @@ class ContractTest < ActiveSupport::TestCase
   should_allow_values_for :discount_type, "$", "%", nil, ''
   should_not_allow_values_for :discount_type, ["amount", "percent", "bar"]
 
-  context "start_date" do
-    should "be before end_date"
+  context "end_date" do
+    should "be after start_date" do
+      @contract = Contract.new(:start_date => Date.today, :end_date => Date.yesterday)
+
+      assert @contract.invalid?
+      assert_equal "must be greater than start date", @contract.errors.on(:end_date)
+    end
   end
 
   should "QUESTION: name be unique"