Alright, this is my first blog EVER! I wanted to start off with a general mark that Christianity has made on history. The link below explains not only the meaning of BC and AD, but also how the concept was adopted. I found it interesting that Jesus was not born in 1 AD, as many believe, but rather it is believed in 6 or 4 BC. Who would have thought that a simple ending to specify a year would have such an impact on today's society? Anyway, the link really details everything.
http://agards-bible-timeline.com/q4_ad_bc_ce.html