When Did Christianity Begin?

It began in Northeast Africa. The oldest form that I am aware of is Ethiopian Orthodox. There are traces of the religion in all worship before it.  answers.ask.com

Christianity officially began during the Nicene Conference in 322-23 A.D. When Jesus died the disciples entered the Upper Room and had a transformation and began to preach, teach and heal. But the religion was not official until the Conference.  answers.ask.com