1 files changed, 44 insertions, 0 deletions
diff --git a/activemodel/lib/active_model/type/date_time.rb b/activemodel/lib/active_model/type/date_time.rb
new file mode 100644
index 0000000000..b068cfc672
--- /dev/null
+++ b/activemodel/lib/active_model/type/date_time.rb
@@ -0,0 +1,44 @@
+module ActiveModel
+  module Type
+    class DateTime < Value # :nodoc:
+      include Helpers::TimeValue
+      include Helpers::AcceptsMultiparameterTime.new(
+        defaults: { 4 => 0, 5 => 0 }
+      )
+
+      def type
+        :datetime
+      end
+
+      private
+
+      def cast_value(string)
+        return string unless string.is_a?(::String)
+        return if string.empty?
+
+        fast_string_to_time(string) || fallback_string_to_time(string)
+      end
+
+      # '0.123456' -> 123456
+      # '1.123456' -> 123456
+      def microseconds(time)
+        time[:sec_fraction] ? (time[:sec_fraction] * 1_000_000).to_i : 0
+      end
+
+      def fallback_string_to_time(string)
+        time_hash = ::Date._parse(string)
+        time_hash[:sec_fraction] = microseconds(time_hash)
+
+        new_time(*time_hash.values_at(:year, :mon, :mday, :hour, :min, :sec, :sec_fraction, :offset))
+      end
+
+      def value_from_multiparameter_assignment(values_hash)
+        missing_parameter = (1..3).detect { |key| !values_hash.key?(key) }
+        if missing_parameter
+          raise ArgumentError, missing_parameter
+        end
+        super
+      end
+    end
+  end
+end