Bloomsday is a commemoration observed annually on June 16th in Dublin and elsewhere to celebrate the life of Irish writer James Joyce and relive the events in his novel Ulysses, all of which took place on the same day in Dublin in 1904. Joyce chose the date because his first outing with his wife-to-be, Nora Barnacle happened on that day, when they walked to the Dublin urban village of Ringsend. The name derives from Leopold Bloom, the protagonist of Ulysses.
Here is a Google map locating the many events organized by Irish cultural centers, arts organizations and enthusiastic individuals to celebrate one of modern literature's most famous dates - June 16th. Locations not marked exactly. Full list of Bloomsday events both in Dublin and worldwide available on the James Joyce Center's website.
James Joyce (Oxford Lives)