[FR] show dates in other calendar format

[vnali]

Description

we use a different calendar type than Gregorian in Iran
https://en.wikipedia.org/wiki/Iranian_calendars
usually in custom twig templates we can use twig extension and we can convert Gregorian date to a Persian date with code like this:

$intl=new IntlDateFormatter('fa_IR@calendar=persian', IntlDateFormatter::FULL, IntlDateFormatter::FULL, 'Asia/Tehran', IntlDateFormatter::TRADITIONAL, 'yyyy/MM/dd HH:mm');
$persian_date = $intl->format($date);

so we convert date like 2019/09/26 to Persian format like 1398/07/04

but in pages like http://craft.samplesite/admin/entries, we have Post Date and craft shows it in Gregorian format like 2019/09/26 and i think this is good to idea to show column date in Persian calendar system like 1398/07/04 - maybe if user language is set to Persian or maybe if there is a calendar type per user and it is set to Persian calendar-

possible solution:
it seems Yii2 support different calendar types:
yiisoft/yii2@cdb7d84
so i tried to add

'locale' => 'fa_IR@calendar=persian',
'calendar' => \IntlDateFormatter::TRADITIONAL, 

to https://github.com/craftcms/cms/blob/develop/src/config/locales/fa.php

but it seems craft ignores calendar type and generate date column in Gregorian anyway.

is it possible to show dates in other calendar format for columns like post date or expiry date?

[vnali]

i saw a commit about this by you @brandonkelly on yii2 repo. could we possibly have this in near future?

[brandonkelly]

@vnali Yeah I’m working on it for 3.4.

[brandonkelly]

Pushing this back to 4.0, because it is going to introduce breaking changes.