That should do the trick:
string time = "Thu Sep 23 19:34:06 IST 2010";
string pattern = "ddd MMM d HH:mm:ss IST yyyy";
IFormatProvider culture = new CultureInfo("en-US", true);
DateTime timeVal;
bool bSuccess = DateTime.TryParseExact(time, pattern, culture, DateTimeStyles.AllowWhiteSpaces, out timeVal);
MessageBox.Show(timeVal.ToString("MM/dd/yyyy"));