16th October, 1843.
On this day, William Hamilton, noted Irish Mathematician, while going for a stroll in dublin had an epiphany as he wandered past Brougham Bridge and, to cut a long story short, solved a complex mathematical puzzle carving the formula: i2 = j2 = k2 = i j k = -1 into the bridge. These quaternions have become the basis of the mathematics behind the projection of movement in 3-d spaces, i.e. robotic arms etc. amongst many other things...
Why Broomsday you ask?
The reasons are twofold. Firstly, in Irish, being the funny language it is, Brougham is in fact pronounced Broom. Secondly, the life and works of another famous son of Dublin, James Joyce, writer of Ulysses, are celebrated on Bloomsday, the day Loepold Bloom took his epic journey through his fair city.
It seems, for Broomsday organisers, the similarity was too hard to resist.