diff --git a/activemodel/CHANGELOG.md b/activemodel/CHANGELOG.md
index 571c050f2fd8b9b81d7f9576b3eb08c4c92c26d7..912b30768316a248cf5f79e3d068ed9379dbe0d2 100644
--- a/activemodel/CHANGELOG.md
+++ b/activemodel/CHANGELOG.md
@@ -1,3 +1,31 @@
+*   Fix year value when casting a multiparameter time hash
+
+    When assigning a hash to a time attribute that's missing a year component
+    (e.g. a `time_select` with `:ignore_date` set to `true`) then the year
+    defaults to 1970 instead of the expected 2000. This results in the attribute
+    changing as a result of the save.
+
+    Before:
+    ```
+    event = Event.new(start_time: { 4 => 20, 5 => 30 })
+    event.start_time # => 1970-01-01 20:30:00 UTC
+    event.save
+    event.reload
+    event.start_time # => 2000-01-01 20:30:00 UTC
+    ```
+
+    After:
+    ```
+    event = Event.new(start_time: { 4 => 20, 5 => 30 })
+    event.start_time # => 2000-01-01 20:30:00 UTC
+    event.save
+    event.reload
+    event.start_time # => 2000-01-01 20:30:00 UTC
+    ```
+
+    *Andrew White*
+
+
 ## Rails 6.0.0.beta1 (January 18, 2019) ##
 
 *   Add `ActiveModel::Errors#of_kind?`.
diff --git a/activemodel/lib/active_model/type/time.rb b/activemodel/lib/active_model/type/time.rb
index b3056b1333a7e6e1180831ad39c23a4c807b9e72..8fba01b86a7c0d7694c615cec64af47aec1e89e2 100644
--- a/activemodel/lib/active_model/type/time.rb
+++ b/activemodel/lib/active_model/type/time.rb
@@ -5,7 +5,7 @@ module Type
     class Time < Value # :nodoc:
       include Helpers::TimeValue
       include Helpers::AcceptsMultiparameterTime.new(
-        defaults: { 1 => 1970, 2 => 1, 3 => 1, 4 => 0, 5 => 0 }
+        defaults: { 1 => 2000, 2 => 1, 3 => 1, 4 => 0, 5 => 0 }
       )
 
       def type
diff --git a/activemodel/test/cases/type/time_test.rb b/activemodel/test/cases/type/time_test.rb
index 3fbae1a1699e536a49afc02351d0d4eab07db655..5c6271241d5c61a91bc323584d9e992fee887294 100644
--- a/activemodel/test/cases/type/time_test.rb
+++ b/activemodel/test/cases/type/time_test.rb
@@ -16,6 +16,7 @@ def test_type_cast_time
 
         assert_equal ::Time.utc(2000,  1,  1, 16, 45, 54), type.cast("2015-06-13T19:45:54+03:00")
         assert_equal ::Time.utc(1999, 12, 31, 21,  7,  8), type.cast("06:07:08+09:00")
+        assert_equal ::Time.utc(2000,  1,  1, 16, 45, 54), type.cast(4 => 16, 5 => 45, 6 => 54)
       end
 
       def test_user_input_in_time_zone
diff --git a/activerecord/test/cases/type/time_test.rb b/activerecord/test/cases/type/time_test.rb
new file mode 100644
index 0000000000000000000000000000000000000000..1a2c47479fec919468a09d89a0bf461896126835
--- /dev/null
+++ b/activerecord/test/cases/type/time_test.rb
@@ -0,0 +1,22 @@
+# frozen_string_literal: true
+
+require "cases/helper"
+require "models/topic"
+
+module ActiveRecord
+  module Type
+    class TimeTest < ActiveRecord::TestCase
+      def test_default_year_is_correct
+        expected_time = ::Time.utc(2000, 1, 1, 10, 30, 0)
+        topic = Topic.new(bonus_time: { 4 => 10, 5 => 30 })
+
+        assert_equal expected_time, topic.bonus_time
+
+        topic.save!
+        topic.reload
+
+        assert_equal expected_time, topic.bonus_time
+      end
+    end
+  end
+end