diff --git a/activesupport/lib/active_support/core_ext/date/calculations.rb b/activesupport/lib/active_support/core_ext/date/calculations.rb
index 04a32edefdaa59fc5bf50b331ce2de65e50dd80c..1fe4ffb8e1a8cd25d4432143add6435e6a90ae67 100644
--- a/activesupport/lib/active_support/core_ext/date/calculations.rb
+++ b/activesupport/lib/active_support/core_ext/date/calculations.rb
@@ -132,7 +132,7 @@ def last_year
   # Short-hand for years_since(1)
   def next_year
     years_since(1)
-  end
+  end unless method_defined?(:next_year)
 
   # Short-hand for months_ago(1)
   def last_month
@@ -142,7 +142,7 @@ def last_month
   # Short-hand for months_since(1)
   def next_month
     months_since(1)
-  end
+  end unless method_defined?(:next_month)
 
   # Returns a new Date/DateTime representing the "start" of this week (i.e, Monday; DateTime objects will have time set to 0:00)
   def beginning_of_week
diff --git a/activesupport/lib/active_support/core_ext/date_time/conversions.rb b/activesupport/lib/active_support/core_ext/date_time/conversions.rb
index ddfa8d610defaeb832c9fae23624b4257c721c93..5f01bc4fd62625cd60813a55ba3e216c6d103704 100644
--- a/activesupport/lib/active_support/core_ext/date_time/conversions.rb
+++ b/activesupport/lib/active_support/core_ext/date_time/conversions.rb
@@ -58,7 +58,7 @@ def readable_inspect
   # Converts self to a Ruby Date object; time portion is discarded
   def to_date
     ::Date.new(year, month, day)
-  end
+  end unless method_defined?(:to_date)
 
   # Attempts to convert self to a Ruby Time object; returns self if out of range of Ruby Time class
   # If self has an offset other than 0, self will just be returned unaltered, since there's no clean way to map it to a Time
@@ -69,12 +69,12 @@ def to_time
   # To be able to keep Times, Dates and DateTimes interchangeable on conversions
   def to_datetime
     self
-  end
+  end unless method_defined?(:to_datetime)
 
   # Converts datetime to an appropriate format for use in XML
   def xmlschema
     strftime("%Y-%m-%dT%H:%M:%S%Z")
-  end if RUBY_VERSION < '1.9'
+  end unless method_defined?(:xmlschema)
   
   # Converts self to a floating-point number of seconds since the Unix epoch 
   def to_f
diff --git a/activesupport/lib/active_support/core_ext/time/conversions.rb b/activesupport/lib/active_support/core_ext/time/conversions.rb
index 94e01597a9e76c1d384a19a927d07a1568fa770d..6d9c080442904a9c2558d3bcfb25d90eea7ce8cc 100644
--- a/activesupport/lib/active_support/core_ext/time/conversions.rb
+++ b/activesupport/lib/active_support/core_ext/time/conversions.rb
@@ -69,7 +69,7 @@ def to_date
   # In this case, it simply returns +self+.
   def to_time
     self
-  end
+  end unless method_defined?(:to_time)
 
   # Converts a Time instance to a Ruby DateTime instance, preserving UTC offset.
   #