* Astronomy

On April 2, 1868, an earthquake with a magnitude between 7.25 and 7.9 rocked the southeast coast of Hawaii. 
http://en.wikipedia.org/wiki/Hawaii_(island)#Earthquakes_and_tsunamis

The 1990 Bishop's Castle earthquake was an earthquake that hit Shropshire, England on 2 April 1990.
http://en.wikipedia.org/wiki/1990_Bishop%27s_Castle_earthquake

Juan Ponce de León led the first European expedition to Florida, which he named.
http://en.wikipedia.org/wiki/Juan_Ponce_de_Le%C3%B3n#First_voyage_to_Florida

Clément Ader (2 April 1841 - 5 March 1925) was a French inventor and engineer 
http://en.wikipedia.org/wiki/Cl%C3%A9ment_Ader

Francesco Maria Grimaldi (2 April 1618 - 28 December 1663) was an Italian Jesuit priest
http://en.wikipedia.org/wiki/Francesco_Maria_Grimaldi

On the 2nd April 1930, Haile Selassie I was proclaimed Neguse Negest ze-'Ityopp'ya, "King of Kings of Ethiopia". 
http://astronomy.activeboard.com/t44051332/haile-selassie-i-1892-1975/

Charlemagne (2 April 742/747/748 - 28 January 814) was the King of the Franks from 768
http://en.wikipedia.org/wiki/Charlemagne

Percy Braybrooke Molesworth (2 April 1867 in Colombo 25 December 1908) was an amateur astronomer.
https://en.wikipedia.org/wiki/Percy_B._Molesworth

NGC 2805 was discovered by William Herschel on the 2nd April 1791.
http://astronomy.activeboard.com/t57188627/ngc-2805/

NGC 3174 was discovered by William Herschel on the 2nd April 1801.
http://astronomy.activeboard.com/t57188619/ngc-3174/

NGC 3397 was discovered by William Herschel on the 2nd April 1801.
http://astronomy.activeboard.com/t57188604/ngc-3397/

NGC 3500 was discovered by William Herschel on the 2nd April 1801.
http://astronomy.activeboard.com/t57188597/ngc-3500/

NGC 3523 was discovered by William Herschel on the 2nd April 1801.
http://astronomy.activeboard.com/t57188589/ngc-3523/

NGC 3549 was discovered by William Herschel on the 2nd April 1789.
http://astronomy.activeboard.com/t57188584/ngc-3549/