DevDemon Credits v2.5.3a includes a deprecated method decode_date which was removed in #eecms v1.9.2.
2 Answers
In ajax.credits.php line 193:
$this->EE->localize->decode_date('%d-%M-%Y %g:%i %A', $row->date))
should be replaced with:
$this->EE->localize->format_date('%d-%M-%Y %g:%i %A', $row->date))