The WTS says:
The only two birthdays the Bible does mention were for rulers who were enemies of God. (WT 1994 July 15, p. 15; cf. Reasoning from the Scriptures 1985 pp. 68, 69)
This statement is incorrect. Other birthdays are mentioned in the Bible and not in any pejorative sense either: Several scholars hold that birthdays ("day") are mentioned in Job 1:4-5. Among them are Albert Barnes, Adam Clarke, Robert Jamieson, Andrew Fausset and David Brown.
The Living Bible's paraphrase of Job 1:4-5 says:
Every year when each of Job's sons had a birthday, he invited his brothers and sisters to his home for celebration. On these occasions they would eat and drink with great merriment. When these birthday parties ended...
Job appears to define the "day" as a birthday in Job 11:1-3.
Nothing in the Bible text indicates that Job's children did anything evil. Their celebration is not portrayed as a pagan practice. And Job does not condemn the celebration. Moreover regarding Job it is said that he was "a man of blameless and upright life...who feared God and set his face against wrongdoing." (Job 1:1) So if God did not approve of observing birthdays Job obviously would not have allowed the celebrations among his children.
The birthday of John the Baptist was also celebrated. The "angel" who announced John's birth said:
And you will have joy and gladness and many will rejoice over his birth. (Luke 1:14) (The New World Translation 1984)
And most importantly, angels in song and glory celebrated the birth of Christ:
But the angel said to them: "Have no fear, for, look! I am declaring to you good news of a great joy that all the people will have, because there was born to you today a Savior, who is Christ [the] Lord, in David's city..." And suddenly there came to be with the angel a multitude of the heavenly army, praising God and saying: "Glory in the heights above to God, and upon earth peace among men of goodwill." (Luke 2:10,11,13,14. NWT)
This positive event was left out of the WTS's consideration because it negates their assertion that only two birthdays are mentioned in the Bible and both in a negative sense!