Adds install date

LeCountdown/AppDelegate.swift

@@ -32,6 +32,10 @@ class AppDelegate : NSObject, UIApplicationDelegate {
 
         Conductor.maestro.cleanup()
         
+        if Preferences.installDate == nil {
+            Preferences.installDate = Date()
+        }
+        
         return true
     }
     

LeCountdown/Utils/Preferences.swift

@@ -8,6 +8,7 @@
 import Foundation
 
 enum PreferenceKey: String {
+    case installDate
     case countdowns
     case stopwatches
     case playConfirmationSound
@@ -32,6 +33,7 @@ class Preferences {
     @UserDefault(PreferenceKey.playCancellationSound.rawValue, defaultValue: true) static var playCancellationSound: Bool
     @UserDefault(PreferenceKey.cloudKitSchemaInitialized.rawValue, defaultValue: false) static var cloudKitSchemaInitialized: Bool
     @UserDefault(PreferenceKey.defaultVolume.rawValue, defaultValue: 0.5) static var defaultVolume: Float
+    @UserDefault(PreferenceKey.installDate.rawValue, defaultValue: nil) static var installDate: Date?
 
     static var hideSilentModeAlerts: Bool {
         return UserDefaults.standard.bool(forKey: PreferenceKey.showSilentModeAlert.rawValue)