Fix id of Items, saving

CHDataManagement/Model/DateItem.swift

@@ -2,7 +2,7 @@ import Foundation
 
 protocol DateItem {
 
-    var id: String { get }
+    var identifier: String { get }
 
     var startDate: Date { get }
 
@@ -20,7 +20,7 @@ extension Sequence where Element: DateItem {
     func sortedByStartDateAndId() -> [Element] {
         sorted { (lhs, rhs) -> Bool in
             if lhs.startDate == rhs.startDate {
-                return lhs.id < rhs.id
+                return lhs.identifier < rhs.identifier
             }
             return lhs.startDate > rhs.startDate
         }