Portal:History of science/Selected anniversaries/April 28
- 1765 - Birth of Sylvestre François Lacroix, French mathematician (b. 1834)
- 1868 - Birth of Georgy Voronoy, Russian mathematician (d. 1908)
- 1902 - Using the ISO 8601 standard Year Zero definition for the Gregorian calendar preceded by the Julian calendar, the one billionth minute since the start of January 1, Year Zero occurs at 10:40 AM on this date
- 1906 - Birth of Kurt Gödel, Austrian mathematician (d. 1978)
- 1932 - A vaccine for yellow fever is announced for use on humans
- 1941 - Birth of K. Barry Sharpless, American chemist, Nobel laureate
- 1946 - Death of Louis Bachelier, French mathematician (b. 1870)
- 1997 - The 1993 Chemical Weapons Convention goes into effect, with Russia, Iraq and North Korea notable nations who have not ratified the treaty
- 1999 - Death of Arthur Leonard Schawlow, American physicist, Nobel laureate (b. 1921)
- 2005 - The Patent Law Treaty goes into effect