@Fedik Any idea?

Which version of the language pack are you using?
The format is converted using four language strings provided by the language pack. You may want to check those:

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"

These are taken from the official pack from https://downloads.joomla.org/de/language-packs/translations-joomla4/downloads/joomla4-french/4-0-6-1 and look correct.

Can you also check what is stored in the database? Should be in the english format (2022-02-10)

It as @Bakual said.

Use default system format for your language.
There not only "calendar format", but also "format for filter", that must be in sync.

If you changing "calendar format" you also must change "format for filter".

hello
1 i update language to last package
2 i update any item to 31/02/2022

when i load item

to load my code i use this
echo HtmlHelper::date($this->item->arbitrary_property_name['date-de-parution']->value, Text::_('DATE_FORMAT_LC3'));
3 format of date in database 2020-01-31 14:03:03

if is set this

display works but wrong date

Please post what value for this language constants on your admin/site:

DATE_FORMAT_CALENDAR_DATE
DATE_FORMAT_CALENDAR_DATETIME
DATE_FORMAT_FILTER_DATE
DATE_FORMAT_FILTER_DATETIME

You can try search them in language override

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"
seems correct

hm yes, strange then why it fail

lol i take many time to find why item is failed ... lol
tahnks for your help

What value for DATE_FORMAT_LC3?
and what happen if you just do echo HTMLHelper::_('date', $blablaDateValue) (without use of format)?

What's the value of DATE_FORMAT_LC3? If you use that for creating your date, it has to be the ISO format?

It seems @Fedik and me just had the same idea. 😄

Since the calendar field apparently stores the date correctly into the database in format YYYY-MM-DD, and the calendar field also correctly shows the date again, something must be wrong with your code to display the date in frontend.
I doubt the issue is the DATE_FORMAT_LC3 either, as that one should not create such issues when being wrong.

I rather suspect your $this->item->arbitrary_property_name['date-de-parution']->value doesn't hold the date as it is in the database but is already transformed to another format, which is why the date function then breaks.
This value has to be in the format YYYY-MM-DD.

hello i think @Bakual you are right
this <?php echo $this->item->arbitrary_property_name['date-de-parution']->value;?> display 10/01/2020 that the good date ...
how i can format it on html output ? can i use joomla format ?

Joomla always expects YYYY-MM-DD. The same as is stored in the database. So you need to check your code why the value is already localised. You probably already applied the date format on that property and now try to apply it a second time, which fails.

ok thanks i close this thank for all