@tecpromotion Can you please help? See related #40364.

So... Unfortunately I don't understand Bulgarian, so I don't know what has been discussed in the bulgarian forum to the other issue, but I also see that the bulgarian language pack is vastly outdated. I logged into crowdin and proposed a fix to the date as well, but I actually don't know the further process for this. What do we do with this issue? The fix has been put up in crowdin, it is not exactly something in the power of the people who manage the issue tracker... Can we close this issue?

I have informed the Bulgarian translator.
Unfortunately, the last release for Joomla 4 was some time ago and there is no package for Joomla 5 yet.

I'm closing this issue, since it is rather a problem of the bulgarian translation and not of the CMS itself. Everything we can do in the CMS repo has been done. Thank you for reporting this.

Fixed!
I replaced the wrong code at /language/bg-BG/joomla.ini file:
DATE_FORMAT_LC="l, d F Y"
DATE_FORMAT_LC1="l, d F Y"
DATE_FORMAT_LC2="l, d F Y H:i"
DATE_FORMAT_LC3="d F Y"
DATE_FORMAT_LC4="d-m-Y"
DATE_FORMAT_LC5="d-m-Y H:i"
DATE_FORMAT_LC6="d.m.Y H:i:s"
DATE_FORMAT_JS1="d-m-y"
DATE_FORMAT_CALENDAR_DATE="%d.%m.%Y"
DATE_FORMAT_CALENDAR_DATETIME="%d.%m.%Y %H:%M:%S"
DATE_FORMAT_FILTER_DATE="d-m-Y"
DATE_FORMAT_FILTER_DATETIME="d-m-Y H:i:s"

...with orginal code:

DATE_FORMAT_LC="l, d F Y"
DATE_FORMAT_LC1="l, d F Y"
DATE_FORMAT_LC2="l, d F Y H:i"
DATE_FORMAT_LC3="d F Y"
DATE_FORMAT_LC4="Y-m-d"
DATE_FORMAT_LC5="Y-m-d H:i"
DATE_FORMAT_LC6="Y-m-d H:i:s"
DATE_FORMAT_JS1="y-m-d"
DATE_FORMAT_CALENDAR_DATE="%Y-%m-%d"
DATE_FORMAT_CALENDAR_DATETIME="%Y-%m-%d %H:%M:%S"
DATE_FORMAT_FILTER_DATE="Y-m-d"
DATE_FORMAT_FILTER_DATETIME="Y-m-d H:i:s"

And everything work correctly. I should I tell bulgarian translation team to fix it.