reluctantly overriding whole execute_callstack_for_multiparameter_attributes method

this fixes issue for Date column types. Damn method is just too
unwieldly and should be refactored in Rails.

spec/validates_timeliness/extensions/multiparameter_handler_spec.rb

@@ -3,19 +3,31 @@ require 'spec_helper'
 describe ValidatesTimeliness::Extensions::MultiparameterHandler do
   let(:employee) { Employee.new }
 
-  it 'should return string value for invalid dates' do
-    instantiate_time_object('birth_date', [2000, 2, 31]).should == '2000-02-31'
+  context "time column" do
+    it 'should return string value for invalid date portion' do
+      multiparameter_attribute(:birth_datetime, [2000, 2, 31, 12, 0, 0])
+      employee.birth_datetime_before_type_cast.should == '2000-02-31 12:00:00'
+    end
+     
+    it 'should return Time value for valid datetimes' do
+      multiparameter_attribute(:birth_datetime, [2000, 2, 28, 12, 0, 0])
+      employee.birth_datetime_before_type_cast.should be_kind_of(Time)
+    end
   end
 
-  it 'should return string value for invalid datetimes' do
-    instantiate_time_object('birth_datetime', [2000, 2, 31, 12, 0, 0]).should == '2000-02-31 12:00:00'
-  end
-   
-  it 'should return Time value for valid datetimes' do
-    instantiate_time_object('birth_datetime', [2000, 2, 28, 12, 0, 0]).should be_kind_of(Time)
+  context "date column" do
+    it 'should return string value for invalid date' do
+      multiparameter_attribute(:birth_date, [2000, 2, 31])
+      employee.birth_date_before_type_cast.should == '2000-02-31'
+    end
+
+    it 'should return Date value for valid date' do
+      multiparameter_attribute(:birth_date, [2000, 2, 28])
+      employee.birth_date_before_type_cast.should be_kind_of(Date)
+    end
   end
 
-  def instantiate_time_object(name, values)
-    employee.send(:instantiate_time_object, name, values)
+  def multiparameter_attribute(name, values)
+    employee.send(:execute_callstack_for_multiparameter_attributes, name.to_s => values)
   end
 end