import CalendarFoundation
    
// Initialize new instance of controller with `dateSelectedBlock`
let calendarVC = CalendarViewController(dateSelectedBlock: { [weak self] date in
    if let date = date {
        // work with received `Date`
    } else {
        // user selected option "Remove date" = `date` is `nil`
    }
})
    
// From you `UIViewController` present it
present(calendarVC, animated: true)