Birthdays are not mentioned until the 13th chapter of the Knowledge book which is 2/3 of the way through the book. Thus a foundation of the resurrection of loved ones, living on a paradise earth, and being in the "last days" has already been established. This one paragraph establishes the so-called scripturalness of not celebrating birthdays.
kl chap. 13 pp. 126-127 Why Living a Godly Life Brings Happiness ***The Bible specifically mentions only two birthday observances, both involving men who did not serve God. (Genesis 40:20-22; Matthew 14:6-11) Since the Scriptures do not reveal the birth date of the perfect man Jesus Christ, why should we give special attention to the birthdays of imperfect humans? (Ecclesiastes 7:1) Of course, godly parents do not await a special day to show their children love. A 13-year-old Christian girl remarked: "My family and I have lots of fun. . . . I?m very close to my parents, and when other kids ask why I don?t celebrate holidays, I tell them that I celebrate every day." Said a Christian youth aged 17: "In our house, gift-giving is all year long." Greater happiness results when gifts are given spontaneously.