AD
When referring to years, AD is short for Anno Domini, which is Latin for “in the year of the Lord.” It means the number of years since the birth of Jesus Christ.
Sometimes, “CE” is used instead, which strips our the religious aspect by referring to “Common Era” or “Current Era.”
Why I Looked It Up
As a kid, I was told it was short for “after death,” which referred to the number of years since Jesus died. This made sense to 10-year-old me, so it stuck.
However, it presents a problem because if BC is the years before Jesus was born, and AD is the years after Jesus died, then that leaves a 33-ish year gap representing the years Jesus was alive.
“In the year of the Lord” refers to the concept that when Jesus was born, everything changed, and from that moment forward, the Earth was now “with the Lord.”