Davidos,
God's call to His people has always been, " Come out from among them," meaning that a Christian whether Jew or Gentile Christians are a separated body belonging to God and are to strive to be that way because the rest of the world hates them. The one thing that the Scriptures teach and warn of is that there will be many who call themselves Christian but are not according to Jesus. Adopting a date is not therefore as venomous as adopting the practices of pagan religions as all that makes a Christian is his or her faith placed on Jesus' work on the cross for them. True Christians therefore try to emulate Him as best they can.