Consistent sorting of output

CHDataManagement/Model/DateItem.swift

@@ -2,6 +2,8 @@ import Foundation
 
 protocol DateItem {
 
+    var id: String { get }
+
     var startDate: Date { get }
 
     var hasEndDate: Bool { get }
@@ -9,6 +11,18 @@ protocol DateItem {
     var potentialEndDate: Date { get }
 }
 
+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.startDate > rhs.startDate
+        }
+    }
+}
+
 extension DateItem {
 
     var endDate: Date? {