Change the default system Calendar

Didn’t know where to post this question.
I want to change the default Gregorian calendar to the ancient Bulgarian calendar

Is there a way I can do that?

EDIT: Or at least some widget or app that would display this calendar.

KOrganizer is supposed to handle multiple calendars.
Probably you can use as widget …

How would I go about making a Bulgarian Calendar using KOrganize?

At this point i know as much as you about it, except i don’t speak Bulgarian to understand naively how that calendar works. I can read some documentation, but is not on my calendar for today …
Probably somebody else, more experienced will pass by and help you out.

Is there a way I can make my own calendar system with KOrganize?