Error in DateTme in this program

private void Form1_Load(object sender, EventArgs e)
       {
           string strDate = "01/10/1981";
           DateTime MyBirthDayDate = Convert.ToDateTime(strDate);
           int Age = CalculateYorAge(MyBirthDayDate);
       }
       public static int CalculateYorAge(DateTime birthDaydate)
       {
           int yearsAge = DateTime.Now.Year - birthDaydate.Year;
           if (DateTime.Now.Month < birthDaydate.Month || (DateTime.Now.Month == birthDaydate.Month && DateTime.Now.Day < birthDaydate.Day))                yearsAge--; return yearsAge;
       }