The EventKit framework allows the applications to access the calendar on iOS Devices. However, before accessing the calendar, we are required to import EventKit framework in our controller.

import EventKit

To add events to a calendar, we first require the user permission to access the calendar. Once the permission is granted, we may use the below-mentioned code to add events to a calendar.

// Pass the date for which event has to be added
func insertEvent(date : NSDate) {  
 //EKEventStore class represents the Calendar database. The application accesses the calendar using     EKEventStore.

       let eventStore : EKEventStore = EKEventStore()
       //Ask for permission to access system calendar
       eventStore.requestAccess(to: EKEntityType.event) { (granted,error) in
            if (granted) &&  (error == nil) {
                print("permission is granted")
                let event:EKEvent = EKEvent(eventStore: eventStore)
                event.title = "TYPE YOUR TITLE HERE"
                event.startDate = date as Date
                event.endDate = date as Date
                event.notes = "This is a test of creating event"
                event.calendar = eventStore.defaultCalendarForNewEvents
                event.addAlarm(EKAlarm.init(relativeOffset: 60.0))
                do {
                    try eventStore.save(event, span: .thisEvent)
                } catch let specError as NSError {
                    print("A specific error occurred: \(specError)")
                } catch {
                    print("An error occurred")
                }
               
                print("Event saved")

            } else {
              print("need permission to create a event")
            }
        }   

}

Hope it works!

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