Question: "What is the meaning of BC and AD (B.C. and A.D.)?"
Answer: It is commonly thought that BC stands for "before Christ" and AD stands for "after death." This is only half correct. How could 1 B.C. have been "before Christ" and 1 A.D. been "after death"? BC does stand for "before Christ." AD actually stands for the Latin phrase "anno domini" which means "in the year of our Lord." The B.C. / A.D. dating system is not taught in the Bible. It actually was not fully implemented and accepted until several centuries after Jesus' death.
It is interesting to note that the purpose of the BC / AD dating system was to make the birth of Jesus Christ the dividing point of world history. However, when the B.C. / A.D. system was being calculated, they actually made a mistake in pinpointing the year of Jesus' birth. Scholars later discovered that Jesus was actually born in around 4-6 BC, not 0 AD. That is not the crucial issue. The birth, life, ministry, death, and resurrection of Christ are the "turning points" in world history. It is fitting, therefore, that Jesus Christ be the separation of "old" and "new." BC was "before Christ" and since His birth, we have been living "in the year of our Lord." Philippians 2:10-11, "That at the name of Jesus every knee should bow, in heaven and on earth and under the earth, and every tongue confess that Jesus Christ is Lord, to the glory of God the Father."