That title is the Latin phrase meaning “in the year of the Lord”, and is why we label our years as A.D. The calendar of the western world is calibrated to that point, efforts to conceal the fact notwithstanding. But no matter what they call it, there is only one reason to have all of history focused on that point in time:
Jesus rose from the dead, as predicted. (w00t x a gazillion!)
A hoax? A delusion? A warm, fuzzy story? How could millions of people over thousands of years be so utterly fooled as to base their calendar on such things? Answer: it wasn’t a hoax. It wasn’t a delusion. It is a fact of history so earth-shattering that not even the Dark Ages could wipe out the memory of it. This one simple fact, attested by both friendly and hostile witnesses, has changed the world, whether the world wanted changed or not.
And consider the fact that the Roman government never ordered an investigation into the alleged breaking of a Roman seal, stealing a body, and failing to execute the guards charged with protecting the tomb. Not even the Jews looked for Jesus’ body! It would have been so simple to prove that the body was stolen, putting this new “sect” away for good, because the disciples who allegedly did the deed were afraid to go anywhere (John 20:19) and so had no opportunity to hide it. These were the same disciples who ran away when Jesus was on trial (Mark 14:50), hardly the type to risk execution at the hands of the Romans. On top of all that, they still didn’t comprehend the fact that Jesus would rise the third day (John 20:9).
These are all very credible reasons to believe that Jesus did in fact rise from the dead, in fulfillment of prophecy. And this same Jesus cited the Old Testament as the Word of God, making all other religious books mere fables and all other gods impostors. The God of the Bible is like no other (Isaiah 46:9-10), the Jesus of the Bible is like no other (Acts 4:11-12), and our calendar is based on no other event.
This day, whether based on a pagan ritual or not, is the day most Christians have chosen to remind us all of who Jesus is and what He did. Ironically, most churches deny this Death and Resurrection every other day of the year, and are now citing “doctrines of demons” in their celebrations! But God will never leave us without a witness, and the truth will never be completely hidden before this very same Jesus will return for His own (Acts 1:11).
How about now, Jesus?