@Salmatas G. Kirtsidis Th. OE

The issue is on the feed generation not in the module. The generated feed contains date in Greek language which of course is invalid.

I saw that you are using K2 for generating the feeds. K2 does not modify the date. The issue probably occurs when Joomla! is trying to format the data before displaying the feed. Ensure that you are using an up to date version of Joomla!. Since you are under Joomla! 2.5 series you should be using 2.5.28.

If you already use the latest version then something is wrong with either your PHP version or your server's setup.

Hello,

My joomla version is already on 2.5.28 and the k2 version on 2.6.9

Ok there is the <pubDate> (on the Greek language of course) in source code but why it doesn't appear on the feeds after burred on feedburner. Is also this "Greek" problem?

Can you indicate me the php joomla file that is responsible to format the data before display in the feed. I think that I translated the labels that use the feeds' php file...

Thank you in advance.

I don't get what you are asking regarding feedburner. The date should not be in Greek, in any case. Regarding the actual code this where Joomla! is converting the date in feeds:
github.com/joomla/joomla-cms/blob/2.5.x/libraries/joomla/document/feed/renderer/rss.php#L209-L214

This is calling the Joomla! date format function:

github.com/joomla/joomla-cms/blob/2.5.x/libraries/joomla/utilities/date.php#L564-L567

Note that is strongly NOT recommended to modify any of the core Joomla! files.

Hello,

I got the problem. In the github.com/joomla/joomla-cms/blob/2.5.x/libraries/joomla/utilities/date.php file there is the "dayToString" function that probably is involved and gets labels from en-GB.ini and el-GR.ini files. So, after I turned the labels in english into el-GR.ini file, the feed is validated. .

There are some minor mistakes in the text of feeds but is still valid. The problem now is that on the frontend the page renders the dates in english but the frontend laguage is set in Greek language

Use this code inside a template override:
Ensure that you have set the format in the module options to :