Convert DateTime to MySQL TimeStamp
startTime.ToString("yyyy-MM-dd hh:mm:ss");

startTime.ToString ("yyyy-MM-dd HH:mm:ss");

MySqlCOmmand cmd=new MySqlCommand(
    "INSERT INTO MyTable(myDate) VALUES(?myDate)", connection);
cmd.Parameters.AddWithValue("?myDate", startTime);
cmd.ExecuteNonQuery();