No, not that Hamilton.
Courtesy of Slate magazine and mathematics journalist Katharine Merow: Today is the anniversary of the great insight that led William Rowan Hamilton to the discovery of quaternions. Details can be found here: http://www.slate.com/articles/health_and_science/science/2016/10/we_should_celebrate_hamilton_day_a_mathematical_holiday_on_oct_16.html
Or the day can be celebrated in song: