get your system date format and convert realted to it :
char sysseparator = Convert.ToChar(CultureInfo.CurrentCulture.DateTimeFormat.DateSeparator);
string date=CultureInfo.CurrentCulture.DateTimeFormat.ShortDatePattern.ToString();
string date1 = '12-12-2013';
date1 = date1.Replace('-', sysseparator);
string[] splt = date1.ToLower().Trim().Split(sysseparator);
date = RemoveDuplicateChars(date.ToLower(), sysseparator.ToString());
date = date.Replace("d", splt[2].PadLeft(2, '0'));
date = date.Replace("m", splt[1].PadLeft(2, '0'));
date = date.Replace("y", splt[0]);