Answer: What would you do if you didn’t want someone to celebrate your birthday? Notice how God makes perfectly clear so many of the things He wants us to do, by explaining them clearly in His Word, the Holy Bible. So, why is it that there is no sign in the Bible that we should celebrate His birthday?
Instead, why do we see that Jesus Christ and His followers commemorated His death annually, through the observance of the Passover? We read Paul’s words: “Therefore purge out the old leaven, that you may be a new lump, since you truly are unleavened. For indeed Christ, our Passover, was sacrificed for us. Therefore let us keep the feast, not with old leaven, nor with the leaven of malice and wickedness, but with the unleavened bread of sincerity and truth” (1 Corinthians 5:7-8).
How important is this Passover observance? In Christ’s own words: “Then He said to them, ‘With fervent desire I have desired to eat this Passover with you before I suffer; for I say to you, I will no longer eat of it until it is fulfilled in the kingdom of God’” (Luke 22:15-16). And why again are we to eat this Passover? “Do this in remembrance of Me” (v. 19).
Yes, if we study Scripture carefully we can get a good idea of Christ’s birthdate, or at least the general season. It would have been not around the Winter Solstice, but rather about two or three months earlier, based on the Gospel accounts of the Temple service of Christ’s uncle, and on the fact that the shepherds, who would be long since indoors by late December, were still outdoors with their flocks when Christ was born. But nowhere are these facts tied to any idea of a birthday observance.
So, maybe what we should commemorate is His death, just as He wanted us to remember!