System.Globalization.CultureInfo calture = new System.Globalization.CultureInfo("fa-IR");
  System.Globalization.DateTimeFormatInfo info = calture.DateTimeFormat;
  info.AbbreviatedDayNames = new string[] { "ی", "د", "س", "چ", "پ", "ج", "ش" };
  info.DayNames = new string[] { "یکشنبه", "دوشنبه", "ﺳﻪشنبه", "چهارشنبه", "پنجشنبه", "جمعه", "شنبه" };
  info.AbbreviatedMonthNames = new string[] { "فروردین", "اردیبهشت", "خرداد", "تیر", "مرداد", "شهریور", "مهر", "آبان", "آذر", "دی", "بهمن", "اسفند", "" };
  info.MonthNames = new string[] { "فروردین", "اردیبهشت", "خرداد", "تیر", "مرداد", "شهریور", "مهر", "آبان", "آذر", "دی", "بهمن", "اسفند", "" };
  info.AMDesignator = "ق.ظ";
  info.PMDesignator = "ب.ظ";
  info.ShortDatePattern = "yyyy/MM/dd";
  info.FirstDayOfWeek = DayOfWeek.Saturday;
  System.Globalization.PersianCalendar cal = new System.Globalization.PersianCalendar();

  typeof(System.Globalization.DateTimeFormatInfo).GetField("calendar", System.Reflection.BindingFlags.Public | System.Reflection.BindingFlags.Instance | System.Reflection.BindingFlags.NonPublic).SetValue(info, cal);
  object obj = typeof(System.Globalization.DateTimeFormatInfo).GetField("m_cultureTableRecord", System.Reflection.BindingFlags.Public | System.Reflection.BindingFlags.Instance | System.Reflection.BindingFlags.NonPublic).GetValue(info);
  obj.GetType().GetMethod("UseCurrentCalendar", System.Reflection.BindingFlags.NonPublic | System.Reflection.BindingFlags.Instance).Invoke(obj, new object[] { cal.GetType().GetProperty("ID", System.Reflection.BindingFlags.Instance | System.Reflection.BindingFlags.NonPublic).GetValue(cal, null) });
  typeof(System.Globalization.CultureInfo).GetField("calendar", System.Reflection.BindingFlags.Public | System.Reflection.BindingFlags.Instance | System.Reflection.BindingFlags.NonPublic).SetValue(calture, cal);
  typeof(System.Globalization.CultureInfo).GetField("calendar", System.Reflection.BindingFlags.Public | System.Reflection.BindingFlags.Instance | System.Reflection.BindingFlags.NonPublic).SetValue(calture, cal);

  System.Threading.Thread.CurrentThread.CurrentCulture = calture;
  System.Threading.Thread.CurrentThread.CurrentUICulture = calture;
  System.Globalization.CultureInfo.CurrentCulture.DateTimeFormat = info;
  System.Globalization.CultureInfo.CurrentUICulture.DateTimeFormat = info;