diff --git a/lib/ews/types/calendar_item.rb b/lib/ews/types/calendar_item.rb
index 40f796da..518868ab 100644
--- a/lib/ews/types/calendar_item.rb
+++ b/lib/ews/types/calendar_item.rb
@@ -9,28 +9,30 @@ class CalendarItem
       recurring?:   [:is_recurring, :text],
       meeting?:     [:is_meeting, :text],
       cancelled?:   [:is_cancelled, :text],
-      duration:   [:duration, :text],
-      time_zone:   [:time_zone, :text],
-      start:   [:start, :text],
-      end:   [:end, :text],
-      location:   [:location, :text],
-      all_day?:   [:is_all_day_event, :text],
+      duration:     [:duration, :text],
+      time_zone:    [:time_zone, :text],
+      start:        [:start, :text],
+      end:          [:end, :text],
+      location:     [:location, :text],
+      all_day?:     [:is_all_day_event, :text],
       my_response_type:   [:my_response_type, :text],
       organizer: [:organizer, :elems, 0, :mailbox, :elems],
+      optional_attendees: [:optional_attendees, :elems ],
       required_attendees: [:required_attendees, :elems ],
       recurrence: [:recurrence, :elems ],
       deleted_occurrences: [:deleted_occurrences, :elems ],
-      modified_occurrences: [:modified_occurrences, :elems ],
-      has_attachments?: [:has_attachments, :text ],
-      attachments: [:attachments, :elems ]
+      modified_occurrences: [:modified_occurrences, :elems ]
    }
 
     CALENDAR_ITEM_KEY_TYPES = {
+      start:        ->(str){DateTime.parse(str)},
+      end:          ->(str){DateTime.parse(str)},
       recurring?:   ->(str){str.downcase == 'true'},
       meeting?:     ->(str){str.downcase == 'true'},
       cancelled?:   ->(str){str.downcase == 'true'},
-      all_day?:   ->(str){str.downcase == 'true'},
+      all_day?:     ->(str){str.downcase == 'true'},
       organizer: :build_mailbox_user,
+      optional_attendees: :build_attendees_users,
       required_attendees: :build_attendees_users,
       deleted_occurrences: :build_deleted_occurrences,
       modified_occurrences: :build_modified_occurrences