public DateTime?GetPaidHolidayDate(SpecialDate special, string year)
        {
            var holiday = PaidHolidays.FirstOrDefault(x => x.AssociatedSpecialDate == special);

            if (holiday != null)
            {
                return(holiday.GetDate(year));
            }
            return(null);
        }
        public DateTime?GetPaidHolidayDate(string name, string year)
        {
            var holiday = PaidHolidays.FirstOrDefault(x => x.Name == name);

            if (holiday != null)
            {
                return(holiday.GetDate(year));
            }
            return(null);
        }