How to design employee leave management system

public bool CheckLeaveStatus(int empid, DateTime date)
    {
        bool temp = false;
        int totalleave = 0;
        string qry = "select joining from profile where profileid=@id";
        MySqlParameter idP = new MySqlParameter("@id", empid);
        DataRow dr = MySqlHelper.ExecuteDataRow(Common.GetConnectionString(), qry, idP);
        if (dr != null)
        {
            DateTime joiningdate = Convert.ToDateTime(dr["joining"]);
            int legaldate = joiningdate.Day;
            if (legaldate <= 15)
            {
                totalleave += 2;
            }
            else
            {
                totalleave += 0;
            }
            //TimeSpan t1 = date - joiningdate;
            int monthspassed = Common.MonthDifference(date, joiningdate);
            if (monthspassed > 3)//then he is allowd to take leave
            {
                int startmonth = joiningdate.Month + 1;
                int endmonth = date.Month;
                int monthdiffernce = endmonth - startmonth;
              /*here i am having problem how can i written logic for two years passed from joiningdate and after that every month again two leaves issued .in this previous leave is not taken care off and leave taken count from new logic because two years passed */
                if (monthdiffernce > 24)
                {
                    monthdiffernce = 24;
                }
                int leaves = (monthdiffernce) * 2;
                int allowedleaves = leaves + totalleave;
                int availablelaves = allowedleaves - LeaveTaken(empid);
                if (availablelaves > 0)
                {
                    temp = true;
                }
            }
            //DateTime previousdate = date.AddYears(-2);
        }
        return temp;
    }
 public int LeaveTaken(int empid)
    {
        try
        {
            int taken = 0;
            string qry = "select count(*) from leavestatus where empid=@id";
            MySqlParameter idP = new MySqlParameter("@id", empid);
            taken = Convert.ToInt32(MySqlHelper.ExecuteScalar(Common.GetConnectionString(), qry, idP));
            return taken;
        }
        catch
        {
            return 0;
        }
    }
    public void AddLeaves(int empid, DateTime date, string status)
    {
        if (status == "L")
        {
            string qry = "insert into leavestatus(empid,takenon)values(@empid,@takenon)";
            MySqlParameter idP = new MySqlParameter("@empid", empid);
            MySqlParameter takenonP = new MySqlParameter("@takenon", date);
            MySqlParameter[] p = { idP, takenonP };
            MySqlHelper.ExecuteNonQuery(Common.GetConnectionString(), qry, p);
        }
    }