How does Christianity derive from Paganism?

Consider the source.  WHY would you believe what atheists say??

Actually it replaces Paganism. Truth and knowledge always replace ignorance.

it doesn't. there's nothing Anti-Christian about celebrating Jesus every day or on every ocassion.

They take the slightest similarities and say that they mean they must be copied.

The Christian God is the only God Who exists and a person can know this with certainty by reciting the rosary attentively every day.

Every Christian was formerly, pagan.

 3"For though we walk in the flesh, we do not war according to the flesh, 4for the weapons of our warfare are not of the flesh, but divinely powerful for the destruction of fortresses. 5We are destroying speculations and every lofty thing raised up against the knowledge of God, and we are taking every thought captive to the obedience of Christ, 6and we are ready to punish all disobedience, whenever your obedience is complete." (2 Corinthians 10:3-6).

Atheists fail to perceive the spiritual struggle going on around them, so they make silly assumptions about what is happening over generations as elements of religious systems seem to be 'absorbed' into Christianity. The above verses explain it better than trying to link Christian religion to paganism. In reality, they have been 'conquered' and their 'fortresses of speculation' destroyed, (the religious systems themselves), while the precious 'thoughts' contained within them have been preserved, reinterpreted and 'liberated' over the successive generations. 

Processes of nature attributed to 'gods' have been revealed as the operations of angels inside a system of divine worship of only the One GOD, an those 'gods' have been fully outed as 'demons,' (fallen angels), masquerading as distinct deities. As each system falls, it releases these 'prisoners' which become like spoils of war. Since they were always divine agencies, they have always belonged to GOD and were merely recovered, their defamation removed and their 'gifts' released from captivity within a defamatory and destructive system by returning proper honor to their interpretations. This becomes part of Christ's ongoing revealed genius and prodigy within the Holy Spirit.

That is why scripture says this:

7"But to each one of us grace was given according to the measure of Christ’s gift.

8Therefore it says,

            “WHEN HE ASCENDED ON HIGH,

            HE LED CAPTIVE A HOST OF CAPTIVES,

            AND HE GAVE GIFTS TO MEN.” (Ephesians 4:7-8).

Anyone who has studied the history of Christianity in historical context can see that it was influenced at every stage by paganism. Judaism does not accept the idea of God having a son; that's purely pagan. Pagans expect their gods to have miraculous births, so a miraculous birth was invented for Jesus. A ritual meal honoring a god is common in pagan religions. The numerology in Christianity also comes from paganism - the same significant numbers appear in both, such as 3 for a trinity, 4 gospels because there are four corners of the earth, 12 followers of the main god, etc.

The customs associated with Christian holidays come from pagan rites, too. There is nothing in Christianity about bringing greenery indoors, lighting the house, exchanging gifts, or having a feast when the days start getting longer again after the winter solstice. All those customs come from pagan traditions. Same with the fertility symbols used at Easter - rabbits and eggs are fertility symbols common to pagan spring celebrations.

Easter came from Ishtar/Ostara/Floralia, Christmas came from Brumalia/Saturnalia/Yule. Virgin Births and Resurrection is from Greek Paganism (Dionysus/Attis).

The Jesus Story for one is a repeat of many pagan stories of course with the morality and spiritual aspect of it all corrupted. For two all the holidays practiced are pagan. The way the altar is set up is pagan. All the symbols were pagan.