using System;
using System.Globalization;
using System.Reflection;
using System.Threading;

public class Cultures
{
public static void InitializePersianCulture()
{
InitializeCulture("fa-ir", new[] { "ی", "د", "س", "چ", "پ", "ج", "ش" },
new[] { "یکشنبه", "دوشنبه", "سه شنبه", "چهارشنبه", "پنجشنبه", "جمعه", "شنبه" },
new[]
{
"فروردین", "اردیبهشت", "خرداد", "تیر", "مرداد", "شهریور", "مهر", "آبان", "آذر", "دی",
"بهمن", "اسفند", ""
},
new[]
{
"فروردین", "اردیبهشت", "خرداد", "تیر", "مرداد", "شهریور", "مهر", "آبان", "آذر", "دی",
"بهمن", "اسفند", ""
}, "ق.ظ. ", "ب.ظ. ", "yyyy/MM/dd", new PersianCalendar());
}

public static void InitializeCulture(string culture, string[] abbreviatedDayNames, string[] dayNames,
string[] abbreviatedMonthNames, string[] monthNames, string amDesignator,
string pmDesignator, string shortDatePattern, Calendar calendar)
{
var calture = new CultureInfo(culture);
var info = calture.DateTimeFormat;
info.AbbreviatedDayNames = abbreviatedDayNames;
info.DayNames = dayNames;
info.AbbreviatedMonthNames = abbreviatedMonthNames;
info.MonthNames = monthNames;
info.AMDesignator = amDesignator;
info.PMDesignator = pmDesignator;
info.ShortDatePattern = shortDatePattern;
info.FirstDayOfWeek = DayOfWeek.Saturday;
var cal = calendar;
var type = typeof(DateTimeFormatInfo);
var fieldInfo = type.GetField("calendar", BindingFlags.Public | BindingFlags.Instance | BindingFlags.NonPublic);
if (fieldInfo != null)
fieldInfo.SetValue(info, cal);
var field = typeof(CultureInfo).GetField("calendar", BindingFlags.Public | BindingFlags.Instance | BindingFlags.NonPublic);
if (field != null)
field.SetValue(calture, cal);
Thread.CurrentThread.CurrentCulture = calture;
Thread.CurrentThread.CurrentUICulture = calture;
CultureInfo.CurrentCulture.DateTimeFormat = info;
CultureInfo.CurrentUICulture.DateTimeFormat = info;
}
}

Unfortunately the problem is that on the server it is not in the normal list of supported calendars so you can't just use the normal formatting of .net you have to construct the result manually (it's a real pain) however, I think it is good now, the month problem was me, I was getting the month number and then indexing the month name array using that, but I needed to do month-1 for the index as it is a 0 based array.

what should for example 13 May 2020 be in Persian ? just so I can test some dates.

We may need to put the months in as resource, I'll let you know how I get on. It is just difficult to test locally as the calendars behave completely differently and all works fine on my local server, so I suspect it is the server version here that is the issue نوشته شده توسط HuwR

1. 13 May 2020 ==== 24 اردیبهشت 1399
2. I think that the Persian calendar is present in the .NET Framework by default and is probably independent of the server calendar. But I don't know how to use it.
Everything is ok but one, just one step away from the rest of the items. And that is the name of the Persian months.

See the above...
Does the table above help?

If we can add the names of the months in the language resources .. maybe the problem will be solved

Month names: