20 February is specially commemorated in the Ahmadiyya Muslim Community with regard to the Prophecy of Musleh-e-Maud [the Promised Reformer]. This prophecy was fulfilled in the person of Hazrat Mirza Bashiruddin Mahmud Ahmad, Khalifatul Masih II (ra).
Ahmadi Muslims living around the world hold jalsas [gatherings] in commemoration of this day. Jamaat-e-Ahmadiyya does not celebrate the birth of Hazrat Mirza Bashiruddin Mahmud Ahmad (ra), on Musleh-e-Maud Day, rather it is commemorated in regard to the fulfilment of a prophecy.
This prophecy was made by Hazrat Mirza Ghulam Ahmad (as), the Promised Messiah, as per divine revelation to prove the superiority and truthfulness of Islam. The prophecy was made on 20 February 1886, three years prior to the birth of Hazrat Mirza Bashiruddin Mahmud Ahmad (ra). It contained a glad-tiding regarding the Promised Son, who was to be a great servant of Islam. This prophecy was also to serve as a sign for the opponents of Islam.