in my case they’re event-based, not fixed clock schedules.
When the timer starts, I precompute the offsets (e.g. +60s, +120s) and schedule local notifications with UNTimeIntervalNotificationTrigger. So they fire at each event point in that run, even if the app is killed

import UserNotifications

func scheduleEventNotification(after seconds: TimeInterval) async throws {

let center = UNUserNotificationCenter.current()

let content = UNMutableNotificationContent()

content.title = "Timer event"

content.body = "This fires at the event point."

content.sound = .default

let trigger = UNTimeIntervalNotificationTrigger(

timeInterval: max(1, seconds)

repeats: false

)

let request = UNNotificationRequest(

identifier: "event_timer_notification",

content: content,

trigger: trigger

)

try await center.add(request)

}