也可以用來判斷日期區遇到日期幾次
也許有更好的可以交流
public static int GetBetweenBirthdayCount(DateTime pFrom, DateTime pTo, DateTime pBirthday)
        {
            int mBirthdayCount = 0;//會過幾次生日
            int TotalYear = pTo.Year - pFrom.Year;//看區間有幾年
            for (int i = 0; i <= TotalYear; i++)
            {
                int y = pFrom.AddYears(i).Year;
                string m = pBirthday.Month.ToString().PadLeft(2, '0');
                string d = pBirthday.Day.ToString().PadLeft(2, '0');
               
                //如果他是生日229的要判斷
                if (m == "02" && d == "29")
                {//四除的盡就算閏年
                    if (y % 4 != 0)
                    {
                        d = "28";
                    }
                }
                DateTime EveryBirthday = DateTime.Parse(y + "-" + m + "-" + d);
                if (pFrom <= EveryBirthday && pTo >= EveryBirthday)
                {
                    mBirthdayCount++;
                }
            }
            return mBirthdayCount;
        }
