How to change default date language?

[none20]

Hi folks!
I wanna change default date language, I already have Polish translation for GetSimple, but it's not containing the date.

For example:
I want to get a creation date on my page using code:

Code:

<?php get_page_date(); ?>

And it gives me:

Wednesday, October 29th, 2014 - 6:14 PM

Is somewhere Polish translation that includes also the "calendar / date " ?