The Promised Reformer Day (Urdu: یوم مصلح موعود, Arabic: يوم المصلح الموعود) is celebrated by Ahmadi Muslims annually on 20 February in remembrance of the prophecy concerning the birth of an "illustrious son" to Mirza Ghulam Ahmad whom the Ahmadis regard as the Promised Messiah and Mahdi, and its fulfilment in the person of Mirza Bashir-ud-Din Mahmud Ahmad, the second Caliph of the Ahmadiyya Muslim Community.
In the 1880s, Mirza Ghulam Ahmad confronted several Hindu leaders who demanded to show them signs in favour of Islam as a living religion.
In response to this, Mirza Ghulam Ahmad travelled to the town of Hoshiarpur where he spent 40 days in seclusion praying for divine signs in favour of Islam over other faiths.
Subsequently, on 20 February 1886 he published a revelation which contained the prophecy concerning the birth of an illustrious son: I confer upon thee a Sign of My mercy according to thy supplications.
A Sign of grace and beneficence is awarded to thee and thou art granted the key of success and victory.
Thus does God speak so that those who desire life may be rescued from the grip of death and those who are buried in the graves may emerge therefrom and so that the superiority of Islam and the dignity of God's word may become manifest unto the people and so that the truth may arrive with all its blessings and falsehood may depart with all its ills, and so that people may understand that I am the Lord of Power, I do whatever I will, and so that they may believe that I am with thee, and so that those who do not believe in God and deny and reject His religion and His Book and His Holy Messenger Muhammad, the chosen one (on whom be peace) may be confronted with a clear sign and the way of the guilty ones may become manifest.
However a few days after this announcement his wife, Nusrat Jehan gave birth to a daughter and his adversaries began alleging that his prophecy was proved false.
On January 12, 1889, Mirza Mahmud Ahmad was born who is believed by the Ahmadiyya Muslim Community to be the promised son and one who according to Ahmadis displayed in his person all the qualities mentioned in the prophecy.