1 files changed, 14 insertions, 5 deletions
diff --git a/activerecord/lib/active_record/attribute_methods/time_zone_conversion.rb b/activerecord/lib/active_record/attribute_methods/time_zone_conversion.rb
index 7abe29c7d5..4c3d5eed4c 100644
--- a/activerecord/lib/active_record/attribute_methods/time_zone_conversion.rb
+++ b/activerecord/lib/active_record/attribute_methods/time_zone_conversion.rb
@@ -41,11 +41,14 @@ module ActiveRecord
                   unless time.acts_like?(:time)
                     time = time.is_a?(String) ? Time.zone.parse(time) : time.to_time rescue time
                   end
-                  time = time.in_time_zone rescue nil if time
-                  changed = read_attribute(:#{attr_name}) != time
-                  write_attribute(:#{attr_name}, original_time)
-                  #{attr_name}_will_change! if changed
-                  @attributes_cache["#{attr_name}"] = time
+                  zoned_time   = time && time.in_time_zone rescue nil
+                  rounded_time = round_usec(zoned_time)
+                  rounded_value = round_usec(read_attribute("#{attr_name}"))
+                  if (rounded_value != rounded_time) || (!rounded_value && original_time)
+                    write_attribute("#{attr_name}", original_time)
+                    #{attr_name}_will_change!
+                    @attributes_cache["#{attr_name}"] = zoned_time
+                  end
                 end
               EOV
               generated_attribute_methods.module_eval(method_body, __FILE__, line)
@@ -59,6 +62,12 @@ module ActiveRecord
             time_zone_aware_attributes && !self.skip_time_zone_conversion_for_attributes.include?(name.to_sym) && column.type.in?([:datetime, :timestamp])
           end
       end
+
+      private
+      def round_usec(value)
+        return unless value
+        value.change(:usec => 0)
+      end
     end
   end
 end