Today we use AD and BC but what about before Christ existed as a reference point? Who decided that Christ would be used as a reference point and when and how did everyone agree? How did trade and record keeping work and stay congruent if different peoples used different years? And if AD/BC stand for After Death and Before Christ then why is 0 AD not the year when Jesus died?
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 02 February; Quartidi 14 Pluviôse, An CCXXX; 13 Bahman of 1400 Solar Hijri; Reiwa 4; 7530 Anno Mundi; the sixth year of Rodrigo Duterte being President.