1 files changed, 50 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..d48598376e
--- /dev/null
+++ b/activemodel/lib/active_model/type/date_time.rb
@@ -0,0 +1,50 @@
+# frozen_string_literal: true
+
+module ActiveModel
+  module Type
+    class DateTime < Value # :nodoc:
+      include Helpers::TimeValue
+      include Helpers::AcceptsMultiparameterTime.new(
+        defaults: { 4 => 0, 5 => 0 }
+      )
+
+      def type
+        :datetime
+      end
+
+      def serialize(value)
+        super(cast(value))
+      end
+
+      private
+
+        def cast_value(value)
+          return apply_seconds_precision(value) unless value.is_a?(::String)
+          return if value.empty?
+
+          fast_string_to_time(value) || fallback_string_to_time(value)
+        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_parameters = (1..3).select { |key| !values_hash.key?(key) }
+          if missing_parameters.any?
+            raise ArgumentError, "Provided hash #{values_hash} doesn't contain necessary keys: #{missing_parameters}"
+          end
+          super
+        end
+    end
+  end
+end