It was created from Pagan beliefs.
Christianity only claimed it recently because of Jesus' birth.
It is said that it was around much before his birth.
So, it is only a coincidence that its a Christian belief puts jesus' death on the 25th of December even though it was much more likely to have happened some time in in our Spring.
Hence it not being a christian holiday.
You really shouldn't believe Wikipedia anyway. They are wrong about more then one thing.