When did Christianity begin?

Public Christianity began on the day of Pentecost, as
described in Acts Chapter two. One could debate this date. For example,
one could say that Christianity began the day Jesus rose from the dead, or
one could say that Christianity began the day Jesus was born, or the day
he began his public ministry. Since “Christianity” is not defined
precisely in the New Testament, one can always debate the day it started
(In fact, the word Christian only appears twice in the New Testament,
being used by outsiders, not the disciples). However, this debate would
probably not be a fruitful one.

The reason I pick this date is two-fold. First, the events in
Acts Chapter two are the first recorded example of salvation in the name
of Jesus Christ being preached to the general public. This was the first
time we have record of the public proclamation of salvation in the name
of Jesus Christ upon repentance and baptism for forgiveness of sins. One
could debate whether anyone was saved before this time, as the Bible is
silent on the issue, but there is simply no other event recorded anywhere
in the New Testament which is even a close second to Acts 2 and the Day of
Pentecost.

Another reason I pick this date is that Jesus pointed to it
very much as a beginning of a new age–some would say the beginning of the
Christian age. The day of Pentecost was when the Holy Spirit was poured
out with power on the disciples in a unique miraculous way. God was
definitely calling attention to the event! We see tongues of fire, people
preaching and being understood in more than ten languages, a great rushing
wind and so forth. On Pentecost, God was clearly trying to get people’s
attention. In Acts 2 we see the fulfillment of the great prophecy of the
coming of the Kingdom in Joel 2:28-32. Peter declared that the events on
Pentecost were a direct fulfillment of this prophecy (Acts 2:16). Jesus
clearly predicted the great pouring out of the Spirit more than once as a
starting point (Acts 1:4-7, Matthew 16:19,) for the kingdom of God on
earth, as did John the Baptist (Matthew 3:11).

Having given my best answer, and pointed out that, in the end,
one can always debate the date when Christianity began, let me discuss the
actual date of this event. For a number of reasons, most notably Luke’s
comment that Jesus was born during the reign of Herod the Great (who died
in 4 or possible 3 BC), we know that Jesus was born in about 6-5 BC.
Given that the crucifixion had to occur in a year when the pre-Passover
Seder feast occurred on a Friday, possible years for the crucifixion are
AD 29 or AD 33. The most likely date, in my opinion, is AD 29. The Day
of Pentecost occurred fifty days after the Passover (and thus the name
Pentecost) and forty-nine days after the Feast of Firstfruits (and thus
the other common name for Pentecost, which is the Feast of Weeks).
Therefore, taking the Day of Pentecost as the day the Christianity began,
it would be 50 days after the Passover (15th of Nisan) in the year AD 29.

I hope this answers your question.

John Oakes, PhD