Please use format datetime only and get your expected result:
DateTime abc = DateTime.Now;
Label3.Text = abc.ToString("MM/DD/YYYY hh:mm:ss tt").Substring(11,11);
This code will help you are alway get the your expected result
txtintime.Text = (ds.Tables[0].Rows[0][5].ToString("MM/DD/YYYY hh:mm:ss tt").Substring(11, 11));