Change date format

You can change the date format in your admin dashboard: Settings > General.

In your css, display for authors has been set to ‘none.’

.single-author .entry-meta .by-author {
    display: none;
}

Were these changes made manually in the code? Are you able to go in and edit them?

You may also be able to find help that’s more specific to the theme you’re using in the theme’s support forums: https://www.ads-software.com/support/theme/twentyeleven

Still duplicates the date. I wanted to show like
Published on Sept 1st 2013

Any hint?

Do not edit the Twenty Eleven theme. First, re-upload a fresh, unpacked, copy of the theme’s folder to wp-content/themes using FTP or whatever file management application your host provides.
https://www.ads-software.com/themes/twentyeleven

Then create a child theme for your changes.

Yes, start clean with a new Twenty Eleven theme and create a child theme from that. It looks likely that someone edited your current theme and entered the date tag twice.

Ok, with all that in mind, where in styles.css can I change the data format?? I am looking but with no luck.

Apart. I did find the author shortcode in the css file, but what value do I put for it to show who posted it??

Thx

The data format?

You can change the date format in your admin dashboard: Settings > General. There’s a screenshot here: Settings General Screen

The problem for the author entry is that display has been set to ‘none.’ If you delete that line in your .css file, the author should show on your page.

.single-author .entry-meta .by-author {
    display: none;
}

It does not matter I change it there, it allways shows the same and duplicate

In that case, the date format values are most likely hard-coded into your php file, and accidentally duplicated as well. It would be best to start over with a new theme and create a child theme for any edits you might want to make to the php files. It’s a bad idea to edit the original theme.