Leifmk
Deity
Picking another arbitrary date to be the new year 0?
It's been tried a fair few times, usually in connection with a political revolution of some sort. It usually doesn't take but a few such calendars still linger on in limited geographic areas. North Korea, for example.
Re-designing the calendar in any meaningful way? Massively inconvenient and expensive as hell. And worse the more legacy systems we have going.