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

1 files changed, 22 insertions, 0 deletions

diff --git a/activerecord/test/cases/type/time_test.rb b/activerecord/test/cases/type/time_test.rb
new file mode 100644
index 0000000000..1a2c47479f
--- /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