A structure for holding and referencing the time of day

TimeOfDay.swift

struct TimeOfDay {
    
    // MARK: Public Properties
    
    var hours: Int
    var minutes: Int
    
    var stringRepresentation: String {
        var stringRepresentation = hours < 10 ? "0" : ""
        stringRepresentation += "\(hours):\(minutes)"
        return stringRepresentation
    }
    
    var displayString: String {
        let dateFormatter = NSDateFormatter()
        // Backing Format
        dateFormatter.dateFormat = "HH:mm"
        dateFormatter.timeZone = NSTimeZone.systemTimeZone()
        dateFormatter.locale = NSLocale.currentLocale()
        if let date = dateFormatter.dateFromString(stringRepresentation) {
            // Display format
            dateFormatter.dateFormat = "h:mm a"
            return dateFormatter.stringFromDate(date)
        } else {
            return ""
        }
    }
    
    // MARK: Initialization
    
    init?(stringRepresentation: String) {
        let components = stringRepresentation.componentsSeparatedByString(":")
        if components.count == 2, let hours = components.first?.toInt(), let minutes = components.last?.toInt() {
            self.hours = hours
            self.minutes = minutes
        } else {
            return nil
        }
    }
    
    init?(date: NSDate) {
        let formatter = NSDateFormatter()
        formatter.locale = NSLocale.currentLocale()
        formatter.timeZone = NSTimeZone.systemTimeZone()
        formatter.dateFormat = "HH:mm"
        let formattedStringRepresentation = formatter.stringFromDate(date)
        self.init(stringRepresentation: formattedStringRepresentation)
    }
    
    // MARK: Date Conversion

    func timeToday() -> NSDate? {
        return timeOnDate(NSDate())
    }
    
    func timeOnDate(date: NSDate) -> NSDate? {
        let calendar = NSCalendar.currentCalendar()
        let dateComponents: NSDateComponents = calendar.components(NSCalendarUnit.CalendarUnitYear | NSCalendarUnit.CalendarUnitMonth | NSCalendarUnit.CalendarUnitDay | NSCalendarUnit.CalendarUnitHour | NSCalendarUnit.CalendarUnitMinute, fromDate: date)
        dateComponents.hour = hours
        dateComponents.minute = minutes
        return calendar.dateFromComponents(dateComponents)
    }
    
}