From OpenSCADAWiki
The World Calendar System
The World Calendar System starts from 5508 before AD and was used on the SLOVISH-ANTIC territory before the jewi-arias occupation with that "Anno Domini" and JewiChristianity. 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.