diff --git a/activesupport/CHANGELOG b/activesupport/CHANGELOG
index 3a66699f737d48835fdf94d158c4ab53fc7eead4..fd0bd573c1de47ed769d63c2eae83d9acd9ea9d7 100644
--- a/activesupport/CHANGELOG
+++ b/activesupport/CHANGELOG
@@ -1,5 +1,7 @@
 *SVN*
 
+* Time, Date and DateTime #advance accept :weeks option.  #9866 [Geoff Buesing]
+
 * Fix Time#years_ago and #years_since from leap days.  #9865 [Geoff Buesing]
 
 * Time and DateTime#advance accept :hours, :minutes, and :seconds options.  #9825 [Geoff Buesing]
diff --git a/activesupport/lib/active_support/core_ext/date/calculations.rb b/activesupport/lib/active_support/core_ext/date/calculations.rb
index 9da7303f273931cede062c849df8915cc08dda2e..61db7e0f12e4d66857ca7e207828f6dfe0f7d606 100644
--- a/activesupport/lib/active_support/core_ext/date/calculations.rb
+++ b/activesupport/lib/active_support/core_ext/date/calculations.rb
@@ -68,11 +68,12 @@ def minus_with_duration(other) #:nodoc:
         end
         
         # Provides precise Date calculations for years, months, and days.  The +options+ parameter takes a hash with 
-        # any of these keys: :months, :days, :years.
+        # any of these keys: :years, :months, :weeks, :days.
         def advance(options)
           d = self
           d = d >> options.delete(:years) * 12 if options[:years]
           d = d >> options.delete(:months)     if options[:months]
+          d = d +  options.delete(:weeks) * 7  if options[:weeks]
           d = d +  options.delete(:days)       if options[:days]
           d
         end
diff --git a/activesupport/lib/active_support/core_ext/date_time/calculations.rb b/activesupport/lib/active_support/core_ext/date_time/calculations.rb
index 9cb7455dec90b4a159975351ac3237bb83ebc087..b672ada7b9809f0aa60433d2084165fea8e52e72 100644
--- a/activesupport/lib/active_support/core_ext/date_time/calculations.rb
+++ b/activesupport/lib/active_support/core_ext/date_time/calculations.rb
@@ -28,7 +28,7 @@ def change(options)
         end
 
         # Uses Date to provide precise Time calculations for years, months, and days.  The +options+ parameter takes a hash with
-        # any of these keys: :years, :months, :days, :hours, :minutes, :seconds.
+        # any of these keys: :years, :months, :weeks, :days, :hours, :minutes, :seconds.
         def advance(options)
           d = to_date.advance(options)
           datetime_advanced_by_date = change(:year => d.year, :month => d.month, :day => d.day)
diff --git a/activesupport/lib/active_support/core_ext/time/calculations.rb b/activesupport/lib/active_support/core_ext/time/calculations.rb
index d594cf21f97093c0fd0727a4ac32dce0969bba0a..7f449aee49b4b35b0f471cd9ee44ecf5846dd0d6 100644
--- a/activesupport/lib/active_support/core_ext/time/calculations.rb
+++ b/activesupport/lib/active_support/core_ext/time/calculations.rb
@@ -72,7 +72,7 @@ def change(options)
         end
 
         # Uses Date to provide precise Time calculations for years, months, and days.  The +options+ parameter takes a hash with
-        # any of these keys: :years, :months, :days, :hours, :minutes, :seconds.
+        # any of these keys: :years, :months, :weeks, :days, :hours, :minutes, :seconds.
         def advance(options)
           d = to_date.advance(options)
           time_advanced_by_date = change(:year => d.year, :month => d.month, :day => d.day)
diff --git a/activesupport/test/core_ext/date_ext_test.rb b/activesupport/test/core_ext/date_ext_test.rb
index beeaa6ce4d86d21db5bc60d3450e70638bece4ed..3ef4744c44959138592b74fcb6f9d1f9814cd7c7 100644
--- a/activesupport/test/core_ext/date_ext_test.rb
+++ b/activesupport/test/core_ext/date_ext_test.rb
@@ -122,11 +122,14 @@ def test_tomorrow
     assert_equal Date.new(2005,3,2),  Date.new(2005,2,28).tomorrow.tomorrow
   end
 
-  def test_plus
+  def test_advance
     assert_equal Date.new(2006,2,28), Date.new(2005,2,28).advance(:years => 1)
     assert_equal Date.new(2005,6,28), Date.new(2005,2,28).advance(:months => 4)
+    assert_equal Date.new(2005,3,21), Date.new(2005,2,28).advance(:weeks => 3)
+    assert_equal Date.new(2005,3,5), Date.new(2005,2,28).advance(:days => 5)
     assert_equal Date.new(2012,9,28), Date.new(2005,2,28).advance(:years => 7, :months => 7)
     assert_equal Date.new(2013,10,3), Date.new(2005,2,28).advance(:years => 7, :months => 19, :days => 5)
+    assert_equal Date.new(2013,10,17), Date.new(2005,2,28).advance(:years => 7, :months => 19, :weeks => 2, :days => 5)
     assert_equal Date.new(2005,2,28), Date.new(2004,2,29).advance(:years => 1) #leap day plus one year
   end
 
diff --git a/activesupport/test/core_ext/date_time_ext_test.rb b/activesupport/test/core_ext/date_time_ext_test.rb
index f79c73536c2fdf86a6ab065f93fa20ab8f8de7e7..f4d5427d0f5d8e5067514cf07ed07e1551d9cc12 100644
--- a/activesupport/test/core_ext/date_time_ext_test.rb
+++ b/activesupport/test/core_ext/date_time_ext_test.rb
@@ -168,8 +168,11 @@ def test_change
   def test_advance
     assert_equal DateTime.civil(2006,2,28,15,15,10), DateTime.civil(2005,2,28,15,15,10).advance(:years => 1)
     assert_equal DateTime.civil(2005,6,28,15,15,10), DateTime.civil(2005,2,28,15,15,10).advance(:months => 4)
+    assert_equal DateTime.civil(2005,3,21,15,15,10), DateTime.civil(2005,2,28,15,15,10).advance(:weeks => 3)
+    assert_equal DateTime.civil(2005,3,5,15,15,10), DateTime.civil(2005,2,28,15,15,10).advance(:days => 5)
     assert_equal DateTime.civil(2012,9,28,15,15,10), DateTime.civil(2005,2,28,15,15,10).advance(:years => 7, :months => 7)
     assert_equal DateTime.civil(2013,10,3,15,15,10), DateTime.civil(2005,2,28,15,15,10).advance(:years => 7, :months => 19, :days => 5)
+    assert_equal DateTime.civil(2013,10,17,15,15,10), DateTime.civil(2005,2,28,15,15,10).advance(:years => 7, :months => 19, :weeks => 2, :days => 5)
     assert_equal DateTime.civil(2001,12,27,15,15,10), DateTime.civil(2005,2,28,15,15,10).advance(:years => -3, :months => -2, :days => -1)
     assert_equal DateTime.civil(2005,2,28,15,15,10), DateTime.civil(2004,2,29,15,15,10).advance(:years => 1) #leap day plus one year
     assert_equal DateTime.civil(2005,2,28,20,15,10), DateTime.civil(2005,2,28,15,15,10).advance(:hours => 5)
@@ -177,7 +180,7 @@ def test_advance
     assert_equal DateTime.civil(2005,2,28,15,15,19), DateTime.civil(2005,2,28,15,15,10).advance(:seconds => 9)
     assert_equal DateTime.civil(2005,2,28,20,22,19), DateTime.civil(2005,2,28,15,15,10).advance(:hours => 5, :minutes => 7, :seconds => 9)
     assert_equal DateTime.civil(2005,2,28,10,8,1), DateTime.civil(2005,2,28,15,15,10).advance(:hours => -5, :minutes => -7, :seconds => -9)
-    assert_equal DateTime.civil(2013,10,3,20,22,19), DateTime.civil(2005,2,28,15,15,10).advance(:years => 7, :months => 19, :days => 5, :hours => 5, :minutes => 7, :seconds => 9)
+    assert_equal DateTime.civil(2013,10,17,20,22,19), DateTime.civil(2005,2,28,15,15,10).advance(:years => 7, :months => 19, :weeks => 2, :days => 5, :hours => 5, :minutes => 7, :seconds => 9)
 
   end
 
diff --git a/activesupport/test/core_ext/time_ext_test.rb b/activesupport/test/core_ext/time_ext_test.rb
index f3e990051096c969ee0166c50424ff028aacca7e..9965e2574a0054a898831545d83825b5bc100be8 100644
--- a/activesupport/test/core_ext/time_ext_test.rb
+++ b/activesupport/test/core_ext/time_ext_test.rb
@@ -242,8 +242,11 @@ def test_utc_change
   def test_advance
     assert_equal Time.local(2006,2,28,15,15,10), Time.local(2005,2,28,15,15,10).advance(:years => 1)
     assert_equal Time.local(2005,6,28,15,15,10), Time.local(2005,2,28,15,15,10).advance(:months => 4)
+    assert_equal Time.local(2005,3,21,15,15,10), Time.local(2005,2,28,15,15,10).advance(:weeks => 3)
+    assert_equal Time.local(2005,3,5,15,15,10), Time.local(2005,2,28,15,15,10).advance(:days => 5)
     assert_equal Time.local(2012,9,28,15,15,10), Time.local(2005,2,28,15,15,10).advance(:years => 7, :months => 7)
     assert_equal Time.local(2013,10,3,15,15,10), Time.local(2005,2,28,15,15,10).advance(:years => 7, :months => 19, :days => 5)
+    assert_equal Time.local(2013,10,17,15,15,10), Time.local(2005,2,28,15,15,10).advance(:years => 7, :months => 19, :weeks => 2, :days => 5)
     assert_equal Time.local(2001,12,27,15,15,10), Time.local(2005,2,28,15,15,10).advance(:years => -3, :months => -2, :days => -1)
     assert_equal Time.local(2005,2,28,15,15,10), Time.local(2004,2,29,15,15,10).advance(:years => 1) #leap day plus one year
     assert_equal Time.local(2005,2,28,20,15,10), Time.local(2005,2,28,15,15,10).advance(:hours => 5)
@@ -251,14 +254,17 @@ def test_advance
     assert_equal Time.local(2005,2,28,15,15,19), Time.local(2005,2,28,15,15,10).advance(:seconds => 9)
     assert_equal Time.local(2005,2,28,20,22,19), Time.local(2005,2,28,15,15,10).advance(:hours => 5, :minutes => 7, :seconds => 9)
     assert_equal Time.local(2005,2,28,10,8,1), Time.local(2005,2,28,15,15,10).advance(:hours => -5, :minutes => -7, :seconds => -9)
-    assert_equal Time.local(2013,10,3,20,22,19), Time.local(2005,2,28,15,15,10).advance(:years => 7, :months => 19, :days => 5, :hours => 5, :minutes => 7, :seconds => 9)
+    assert_equal Time.local(2013,10,17,20,22,19), Time.local(2005,2,28,15,15,10).advance(:years => 7, :months => 19, :weeks => 2, :days => 5, :hours => 5, :minutes => 7, :seconds => 9)
   end
 
   def test_utc_advance
     assert_equal Time.utc(2006,2,22,15,15,10), Time.utc(2005,2,22,15,15,10).advance(:years => 1)
     assert_equal Time.utc(2005,6,22,15,15,10), Time.utc(2005,2,22,15,15,10).advance(:months => 4)
+    assert_equal Time.utc(2005,3,21,15,15,10), Time.utc(2005,2,28,15,15,10).advance(:weeks => 3)
+    assert_equal Time.utc(2005,3,5,15,15,10), Time.utc(2005,2,28,15,15,10).advance(:days => 5)
     assert_equal Time.utc(2012,9,22,15,15,10), Time.utc(2005,2,22,15,15,10).advance(:years => 7, :months => 7)
     assert_equal Time.utc(2013,10,3,15,15,10), Time.utc(2005,2,22,15,15,10).advance(:years => 7, :months => 19, :days => 11)
+    assert_equal Time.utc(2013,10,17,15,15,10), Time.utc(2005,2,28,15,15,10).advance(:years => 7, :months => 19, :weeks => 2, :days => 5)
     assert_equal Time.utc(2001,12,27,15,15,10), Time.utc(2005,2,28,15,15,10).advance(:years => -3, :months => -2, :days => -1)
     assert_equal Time.utc(2005,2,28,15,15,10), Time.utc(2004,2,29,15,15,10).advance(:years => 1) #leap day plus one year
     assert_equal Time.utc(2005,2,28,20,15,10), Time.utc(2005,2,28,15,15,10).advance(:hours => 5)
@@ -266,7 +272,7 @@ def test_utc_advance
     assert_equal Time.utc(2005,2,28,15,15,19), Time.utc(2005,2,28,15,15,10).advance(:seconds => 9)
     assert_equal Time.utc(2005,2,28,20,22,19), Time.utc(2005,2,28,15,15,10).advance(:hours => 5, :minutes => 7, :seconds => 9)
     assert_equal Time.utc(2005,2,28,10,8,1), Time.utc(2005,2,28,15,15,10).advance(:hours => -5, :minutes => -7, :seconds => -9)
-    assert_equal Time.utc(2013,10,3,20,22,19), Time.utc(2005,2,28,15,15,10).advance(:years => 7, :months => 19, :days => 5, :hours => 5, :minutes => 7, :seconds => 9)
+    assert_equal Time.utc(2013,10,17,20,22,19), Time.utc(2005,2,28,15,15,10).advance(:years => 7, :months => 19, :weeks => 2, :days => 5, :hours => 5, :minutes => 7, :seconds => 9)
   end
 
   def test_next_week