Unlike many other languages, Persian does not use the Latin digits (1, 2, 3, ...) but its own digits (۱, ۲, ۳, ...)

I will explain the bug using an example: In https://www.wikidata.org/wiki/Q95963597?uselang=fa the date values for properties P571 and P585 are using the correct digits for the day of the month (such as "۱۷ مارس" for "17 March") but not for the year ("2020" should be shown as "۲۰۲۰" but isn't). Screenshot below.

The problem also appears when you try to edit the data:

Unfortunately, I am unfamiliar with the Wikibase/Wikidata world so I cannot say which part of code is responsible for this. It is surprising to me though, because we have MW code functions for displaying dates in localized format, and it appears that we are not using those in Wikibase.

Note that the issue is not restricted to this particular item or property, and impacts all date properties on all items.