     func calendar(calendar : JTAppleCalendarView, isAboutToDisplayCell cell: JTAppleDayCellView, date:NSDate, cellState: CellState) {}
     func calendar(calendar : JTAppleCalendarView, isAboutToResetCell cell: JTAppleDayCellView){}
     func calendar(calendar : JTAppleCalendarView, isAboutToDisplaySectionHeader header: JTAppleHeaderView, dateRange: (start: NSDate, end: NSDate), identifier: String) {}
-    func calendar(calendar : JTAppleCalendarView, sectionHeaderIdentifierForDate dateRange: (start: NSDate, end: NSDate), belongingTo month: Int) -> String {return ""}
+    func calendar(calendar : JTAppleCalendarView, sectionHeaderIdentifierForDate dateRange: (start: NSDate, end: NSDate), belongingTo month: Int) -> String? {return nil}
     func calendar(calendar : JTAppleCalendarView, sectionHeaderSizeForDate dateRange:(start: NSDate, end: NSDate), belongingTo month: Int) -> CGSize {return CGSizeZero}
 }
 

        switch cellSource {
        case let .fromXib(xibName):
            let viewObject = NSBundle.mainBundle().loadNibNamed(xibName, owner: self, options: [:])
            guard let view = viewObject?[0] as? ViewType else {
                print("xib: \(xibName),  file class does not conform to the JTAppleViewProtocol")
                assert(false)
                return
            }
            self.view = view
            break
        case let .fromClassName(className):

    ///     - date: Contains the startDate and endDate for the header that is about to be displayed
    /// - Returns:
    ///   String: Provide the registered header you wish to show for this date
    func calendar(calendar : JTAppleCalendarView, sectionHeaderIdentifierForDate dateRange: (start: NSDate, end: NSDate), belongingTo month: Int) -> String?
    /// Implement this function to use headers in your project. Return the size for the header you wish to present
    /// - Parameters:
    ///     - date: Contains the startDate and endDate for the header that is about to be displayed
