Wikipedia on Broom (or Broome, or Brougham) Bridge,
where on 16 October 1843 Hamilton discovered quaternions:
"The 16 October is sometimes referred to as
Broomsday (in reference to Broome Bridge)
and as a nod to the literary commemorations
on 16 June (Bloomsday in honour of James Joyce)."
See also, in this journal, The Craft.