Use a localized string

Samples/Swift/DaysUntilBirthday/Shared/ViewModels/BirthdayViewModel.swift

@@ -24,11 +24,15 @@ final class BirthdayViewModel: ObservableObject {
   @Published private(set) var birthday: Birthday?
   /// Computed property calculating the number of days until the current user's birthday.
   var daysUntilBirthday: String {
-    guard let bday = birthday?.date else { return "No birthday" }
+    guard let bday = birthday?.date else {
+      return NSLocalizedString("No birthday", comment: "User has no birthday")
+    }
     let now = Date()
     let calendar = Calendar.autoupdatingCurrent
     let dayComps = calendar.dateComponents([.day], from: now, to: bday)
-    guard let days = dayComps.day else { return "No birthday" }
+    guard let days = dayComps.day else {
+      return NSLocalizedString("No birthday", comment: "User has no birthday")
+    }
     return String(days)
   }
   private var cancellable: AnyCancellable?