diff --git a/plugins/custom_forms/lib/custom_forms_plugin/form.rb b/plugins/custom_forms/lib/custom_forms_plugin/form.rb
index 9426f97..8225c7d 100644
--- a/plugins/custom_forms/lib/custom_forms_plugin/form.rb
+++ b/plugins/custom_forms/lib/custom_forms_plugin/form.rb
@@ -10,6 +10,7 @@ class CustomFormsPlugin::Form < Noosfero::Plugin::ActiveRecord
 
   validates_presence_of :profile, :name
   validates_uniqueness_of :slug, :scope => :profile_id
+  validate :period_range, :if => Proc.new { |f| f.begining.present? && f.ending.present? }
   validate :access_format
 
   before_validation do |form|
@@ -75,4 +76,8 @@ class CustomFormsPlugin::Form < Noosfero::Plugin::ActiveRecord
       end
     end
   end
+
+  def period_range
+    errors.add(:base, _('The time range selected is invalid.')) if ending < begining 
+  end
 end
diff --git a/plugins/custom_forms/test/unit/custom_forms_plugin/form_test.rb b/plugins/custom_forms/test/unit/custom_forms_plugin/form_test.rb
index f56a29e..bee84c0 100644
--- a/plugins/custom_forms/test/unit/custom_forms_plugin/form_test.rb
+++ b/plugins/custom_forms/test/unit/custom_forms_plugin/form_test.rb
@@ -53,6 +53,20 @@ class CustomFormsPlugin::FormTest < ActiveSupport::TestCase
     assert !form.errors.invalid?(:slug)
   end
 
+  should 'validate the difference between ending and beginning is positive' do
+    profile = fast_create(Profile)
+    form = CustomFormsPlugin::Form.new(:profile => profile, :name => 'Free Software')
+
+    form.begining = Time.now
+    form.ending = Time.now + 1.day
+    assert form.valid?
+    assert !form.errors.invalid?(:base)
+
+    form.ending = Time.now - 2.day
+    assert !form.valid?
+    assert form.errors.invalid?(:base)
+  end
+
   should 'define form expiration' do
     form = CustomFormsPlugin::Form.new
     assert !form.expired?
--
libgit2 0.21.2