setlocale in gsconfig.php - date is not correct

[JP]

I see that you test it on local webserver.
Is your webserver configured correctly to operate with setlocale (does it contain CZ)?

Other specific function Czech display is right.

Screenie you posted shows date of added page in plain GS, or is it a content posted using an additional plugin ?

Both - plain GS (date of entry) and plugin (Calendar - Events).

I'd firstly try to look how does it work on my hosting provider's server.

Not working - same as the local webserver.

ps. try to use strftime with your own date display setting.

I do not understand...

P.S. maybe the error is in the date_default_timezone_set?