For those who care, the person that posted this thread rejects the Trinity, the bodily resurrection, and other essential doctrines that define the historic Christian faith. You will find most of what he believes by googling "cults", "Armstrongism", or "Herbert W. Armstrong".
Unfortunately those who observe it do it at the expense of the very same holy days that Jesus Christ created, observed, and commanded his followers to observe:
Lev 23:2 Speak unto the children of Israel, and say unto them, Concerning the feasts of the LORD, which ye shall proclaim to be holy convocations, even these are my feasts.
Lev 23:4 These are the feasts of the LORD, even holy convocations, which ye shall proclaim in their seasons.
These feast days, God's feast days, Jesus's feast days, are listed in the rest of Leviticus 23.
Boy, oh boy! You got me there!
God ordained His Sabbaths and Holy days in Leviticus 23 to be observed forever "In all your generations". Our Saviour and the Apostles observed these same events as we are commanded to do also. You may search the scriptures from Leviticus to Revelation and will not find one reference by anyone telling us these Sabbaths and Holy Days have been done away with. These are the celebrations of The Lord.
However, from the middle of the first century we see both Luke and Paul discuss the significance of the birth of Jesus and that is in the New Testament and worthy of commemorating.
Sure...His birth was very significant....but the only Biblical examples of birthday celebrations are [Genesis 40:20]; [Matthew 14:6] and [Mark 6:21]. On both occasions it marked an execution for someone....a hanging in the Old and a beheading in the New! Nice examples!
If the Lord wanted the birth to be a remembrance, he and the Apostles would have lead by example. They didn't.