Post Date Displaying Incorrectly

Hi,

On this site I look after:
https://www.altrincham-interfaith.org.uk/

The post date is displaying incorrectly – on all posts it just says:

Posted on rd June 2012 by admin

Instead of showing the date.

I have compared the “twentyten_posted_on()” function on the twentyten theme on this site, and another one where it works fine, and they’re the same.

I have looked at the database table where the post dates are stored, and they look fine as well.

I can’t work out why it’s dropping the numeric day that the entry was posted on.

Any advice much appreciated.

Thanks!