string d = "20090803112440328";
string[] s = new string[7];
s[0] = d.Substring(0, 4);
s[1] = d.Substring(4, 2);
s[2] = d.Substring(6, 2);
s[3] = d.Substring(8, 2);
s[4] = d.Substring(10, 2);
s[5] = d.Substring(12, 2);
s[6] = d.Substring(14, 3);
DateTime dt=Convert.ToDateTime(s[0]+"-"+s[1]+"-"+s[2]);
dt= dt.AddHours(int.Parse(s[3]));
dt = dt.AddMinutes(int.Parse(s[4]));
dt = dt.AddSeconds(int.Parse(s[5]));
dt = dt.AddMilliseconds(int.Parse(s[6]));
Response.Write(dt.ToString());