Iwan Petrowitsch Kulibin was born on 21st April, 1735 in Nizhny Novgorod.
Philippe Samuel LeCoultre was born on 21st April, 1780 in Le Chenit.
Louis Fortin was born on 21st April, 1797 in Saint-Nicolas d'Aliermont.
Auguste Audemars was born on 21st April, 1806.
Julien Hilaire Rodanet was born on 21st April, 1810 in Rochefort, Charente-Maritime.
Cyprien (Paulin) Paquet was born on 21st April, 1817 in Saint-Nicolas d'Aliermont.
Éléontine-Olive Denis was born on 21st April, 1835 in Saint-Nicolas d'Aliermont.
Hippolyte-Adonis Dumouchel was born on 21st April, 1836 in Saint-Nicolas d'Aliermont.
Charles Henri Meylan was born on 21st April, 1842 in Le Sentier.
Karl Wilhelm Höhnel was born on 21st April, 1885 in Altenberg (Saxonia).
Eberhard Baron was born on 21st April, 1937 in Wangern, Kreis Breslau.