Did I find a problem or did I not understand correctly? (Validation with Annotations)

Hi Community,
I am testing CommunityToolkit.mvvm and I have some problems ...
#1
I have a property of type string that must contain an EmailAddrtes

This is the property definition:
[ObservableProperty]
[NotifyDataErrorInfo]
[Required]
[EmailAddress]
public string? _mailAddress;

This is working perfectly

But I also have a string property that should contain a date, but I can't get the correct validation.

This is the definition:
[ObservableProperty]
[NotifyDataErrorInfo]
[Required]
[DataType(DataType.DateTime)] // Doesn't work
[DisplayFormat(DataFormatString = "{0:yyyy-MM-dd}", ApplyFormatInEditMode = true)] // Doesn't work
public string? _birthDate2;

I think the problem is in the annotation:
[DataType(DataType.DateTime)]

But what do I have to write to get the correct validation?

#2
In addition to validation, I would also like to get the required formatting,
but that doesn't seem to work either.

#3
A general problem, not specifically of the toolkit.
When I search for something on GitHub / NuGet I find dozens of occurrences of packages of similar name...
Wouldn't it be appropriate to assign a unique identifier so that the poor programmer knows which one to choose?
Thank you for your attention.

Best regards