Gnatt chart- JpGraph locale Error

You need to edit the file: jpgraph.php (Most probably path will be lib/jpgraph/src/jpgraph/jpgraph.php)

Modify the following code in jpgraph.php
$res = @setlocale(LC_TIME, $aLocale);

and change it to:
$res = @setlocale(LC_TIME, "pt_BR"); //Put the corresponding locale. Here it is "pt_BR".

You can find the locale details using the code:
system('locale -a'); // for all locales
?>