From OpenSCADAWiki
The World Calendar System
The World Calendar System starts from 5508 before AD and was used in the SLOVISH-ANTIC territory before the jewish occupation with that "Anno Domini" and JewChristianity. This Calendar System was used here in parallel up to XVIII century, so its was appended to TDE by the patches kcalendarsystem_World.patch in tdelibs-trinity and tdebase-trinity, initially in a simple form.