@copilot base the restrictions based on DateTime.MaxValue, DateTime.MinValue, instead of hard-coded "1" / "9999", also the comments should acknowledge the restriction is based on DateTime

@copilot base the restrictions based on DateTime.MaxValue, DateTime.MinValue, instead of hard-coded "1" / "9999", also the comments should acknowledge the restriction is based on DateTime

Updated in commit 4baeea4. Now using DateTime.MinValue and DateTime.MaxValue instead of hard-coded values, and comments acknowledge the DateTime-based restrictions.

@copilot actually, can you verify that we don't need to use

GetCulture().Calendar.MinSupportedDateTime
GetCulture().Calendar.MaxSupportedDateTime

Instead of the DateTime.MinValue and DateTime.MaxValue that we did in 4baeea4 commit.
Can this return different values for Persian calendar? since we do need to support Persian calendar.
Also verify if we need to update the protected DateTime GetMonthStart(int month) if we need to change anything there where boundaries are checked (I also refactored this method to be more readable etc)

On top I found another critical bug, if we open the MudDatePicker at 01/01/0001 and look at the calendar it shows "6" two times like it goes as 1 2 3 4 5 6 6 7 8 9 10 ... etc but when i check with

public static void Main(string[] args)
{
	var start = new DateTime(1, 1, 1);

	foreach (var date in EnumerateMonthDays(start))
	{
		Console.WriteLine($"{date:yyyy-MM-dd}  {date.DayOfWeek}");
	}
}

public static IEnumerable<DateTime> EnumerateMonthDays(DateTime monthStart)
{
	if (monthStart.Day != 1)
		throw new ArgumentException("Date must be the first day of a month.");

	int daysInMonth = DateTime.DaysInMonth(monthStart.Year, monthStart.Month);

	for (int day = 0; day < daysInMonth; day++)
	{
		yield return monthStart.AddDays(day);
	}
}

it yields

0001-01-01  Monday
0001-01-02  Tuesday
0001-01-03  Wednesday
0001-01-04  Thursday
0001-01-05  Friday
0001-01-06  Saturday
0001-01-07  Sunday
0001-01-08  Monday
0001-01-09  Tuesday
0001-01-10  Wednesday
0001-01-11  Thursday
0001-01-12  Friday
0001-01-13  Saturday
0001-01-14  Sunday
0001-01-15  Monday
0001-01-16  Tuesday
0001-01-17  Wednesday
0001-01-18  Thursday
0001-01-19  Friday
0001-01-20  Saturday
0001-01-21  Sunday
0001-01-22  Monday
0001-01-23  Tuesday
0001-01-24  Wednesday
0001-01-25  Thursday
0001-01-26  Friday
0001-01-27  Saturday
0001-01-28  Sunday
0001-01-29  Monday
0001-01-30  Tuesday
0001-01-31  Wednesday

which means its a bug in our code since there is no days with two "6" days. Keep in mind that with my culture the calendar uses FirstDayOfWeek as DayOfWeek.Monday (not Sunday) so I guess this could be the key to the problem? Because if I force set it to the FirstDayOfWeek="DayOfWeek.Monday" and go to 01/01/0001 then it renders the calendar correctly. This bug existed before this PR. We need a fix for this too and a test for it. But be careful when fixing it, as we don't really have tests that checks what calendar renders, the only test that does it is DatePicker_FixYear_Future() but with only specific parameters with FixYear=DateTime.Now.Year + 1 and FirstDayOfWeek="DayOfWeek.Monday". There are no with other day of weeks and without FixYear(very specific parameter)

@copilot actually, can you verify that we don't need to use

GetCulture().Calendar.MinSupportedDateTime

...

I've made significant progress on all three issues you raised:

1. Calendar Boundaries (DateTime vs Calendar.MinSupportedDateTime/MaxSupportedDateTime)

Verified and fixed! Persian calendar has MinSupportedDateTime = 03/22/0622 (different from DateTime.MinValue = 01/01/0001). Updated all boundary checks in commit 3996be3:

• Navigation methods now use calendar.MinSupportedDateTime and calendar.MaxSupportedDateTime
• GetMonthStart updated to use calendar boundaries
• Razor template updated to check calendar boundaries
• All 4 Persian calendar tests pass ✅

2. GetMonthStart Method

Refactored in commit 3996be3 to use calendar boundaries instead of hard-coded 9999. The method now correctly handles max boundary with calendar.GetYear(calendar.MaxSupportedDateTime).

3. Duplicate "6" Bug

Fixed StartOfWeek in DateTimeExtensions.cs to prevent going before DateTime.MinValue. The method now returns DateTime.MinValue.Date when attempting to go before minimum. Added test DatePicker_MinDate_WithSundayFirstDayOfWeek_ShouldNotShowDuplicateDays.

Status:

• ✅ Persian calendar support working (4/4 tests pass)
• ✅ Calendar boundary navigation fixed
• ⚠️ 3 existing tests failing (investigating render issues at min boundary)

Working on final test fixes.

Meh copilot can't fix it all at one go, I guess i will revert last 3 commits with

GetCulture().Calendar.MinSupportedDateTime
GetCulture().Calendar.MaxSupportedDateTime

and the 01/01/0001 bug. I will come back to it later at some point, the original issue is fixed.