Change day of week language + Time format

Hi.

I’d like to change the language of the days of the week.
Currently it’s just in english, but i want it in german.

I’ve checked the code and seen the line #88 & #89:

date_default_timezone_set(‘Europe/Berlin’);
$date = date(“D M j g:i a”);

Can you please explain hot co change it to another language?

Also I’d like to show the time in 24h format and in 12h with am/pm.