Calendars supports up to 5 reminders for each event. To add a default alert, which will be applied automatically to all newly created events: Tap Settings.
Tap Alert options.
Tap Add Default Reminder....
To turn on alarms in Calendars, you should enable them. For this, follow the steps below: Tap Settings.
Tap Alert options.
Select an alarm sound instead of No Sound. After that, go to the Notifications tab in iPhone/iPad Settings > Find the Calendars app in the list > Notifications > Enable Allow Notifications toggle > Enable all the nec...