If you want to setup calendar alarms to be notified of upcoming birthdays on your iPhone or iPad, or you’re simply tired of entering alarms individually when creating events, you’ll be happy to know that you can actually set default reminders for all new events in the iOS Settings app.
Simply go into Mail, Contacts, Calendars and scroll down to the “Calendars” section and tap Default Alert Times.
You’ll see options here to set default alerts separately for birthdays, normal events, and all-day events.