The Christian BC/AD calendar is just one amongst many possible systems of year counting. Various other alternative calendars exist, as we can see from the appropriate section of the FAQ, Other Dating Systems under Calendars, if your browser doesn't automatically take you there.

Indeed, BC/AD is simply a regnal calendar that refuses to change eras like normal regnal calendars. Multiple other calendar systems remain in use today. Japan still uses a regnal calendar for official purposes.

Posted on this day, Wednesday March 22; Duodi 2 Germinal, An CCXXX; 2 Farvardin of 1400 Solar Hijri; Reiwa 4; 7530 Anno Mundi; the sixth year of Rodrigo Duterte being President.