Date format should be taken from somewhere or (preferably) configured in the `settings.inc.php`.

`$value->txt` has to be escaped.
Definitely `htmlspecialchars`, probably `strip_tags`, and depending on the log text content `nl2br`. (I didn’t check the log format yet.)
If `strip_tags` is used, `htmlspecialchars` is probably not needed any more.
* http://php.net/manual/en/function.htmlspecialchars.php
* http://www.php.net/manual/en/function.strip-tags.php
* http://www.php.net/manual/en/function.nl2br.php