May 21

Regarding the birth of this servant, which also happened on that day, [23 May 1844] this a proof of the favors and bounties of God toward this servant. However, this Blessed Day must be known as the Day of the Declaration of His Highness the Supreme (BAB) and the beginning of the effulgence of the Sun of Reality. You must on this account be engaged in rejoicing, happiness and gladness. This is the truth! Beware! Beware! that you avoid that which is mentioned; otherwise, it will cause the utmost grief to the heart of Abdul-Baha. 
- ‘Abdu'l-Baha  (Tablets of Abdu'l-Baha vol. 3)