Depending on your installation of PHP you might have support for several locales. By default the locale is set up to use the default locale on the server.
To specifically set a locale you specify the wanted locale with a locale string (ala standard PHP), for example American English is specified with the string 'EN_US', British English with 'EN_UK' 'nl_NL' for Dutch and so on. If your current installation does not support the specified locale an error message will be given.
$graph ->scale->SetDateLocale( "se_SE");
The result is displayed below.