All of the languages show English time and date for me. I tried to get untranslated strings but nothing about date and time showed up.
apps/frappe/frappe/public/js/frappe/misc/pretty_date.js or moment with locates - I guess one of these files handle the date/time format.
and in frappe translate is translated correctly . but it dos not change when i change main lang of the system
what the best practice to make it translated correctly based on lang ??