pubDate has invalid year format

Same request from me.
The two digits year is not reported as incorrect though, but "problematical".
The feed validates but "interoperability with the widest range of feed readers could be improved", which woud rather be appreciated...

Why is \DateTimeInterface::RSS not used since it exists?

@pbouchereau Good call. I have update the branch.

I can verify the same issue. In our case the problem seems to be only with the channel pubDate. Actual item pubDates are correct because we have set a different date format in the field settings.

At the moment the MR pipeline seems to be failing also and I cannot seem to apply the patch either against 2.3 or 2.x-dev branch.

Gathering patches for root package.
Loading composer repositories with package information
Updating dependencies
Lock file operations: 0 installs, 1 update, 0 removals
  - Upgrading drupal/views_rss (2.3.0 => dev-2.x 7f1e77a)
Writing lock file
Installing dependencies from lock file (including require-dev)
Package operations: 1 install, 0 updates, 0 removals
  - Syncing drupal/views_rss (dev-2.x 7f1e77a) into cache
Gathering patches for root package.
Gathering patches for dependencies. This might take a minute.
  - Installing drupal/views_rss (dev-2.x 7f1e77a): Cloning 7f1e77a4f2 from cache
  - Applying patches for drupal/views_rss
    assets/patches/3492994--views-rss--rss-date-format.diff (#3492994 Change date format for RSS feed)
   Could not apply patch! Skipping. The error was: Cannot apply patch assets/patches/3492994--views-rss--rss-date-format.diff

I tested this patch and I encountered an error where the current date format D, d M Y H:i:s O gets translated based on the Drupal site language.

When previewing the date format in fi/admin/config/regional/date-time/formats/manage/rfc822_rss it gets translated as Ma, 03 Maa 2025 12:17:14 +0200 and this seems to break the feed and we get a validation error
"Failed to read requested Feed information. Details: Error in line 15 position 52. An error was encountered when parsing a DateTime value in the XML. clientRequestId: f40f103e-0cb9-4cc4-9d4d-827e9031b7c1"