There is something slightly bizarre about the celebration of the centenary of a non-existent event. So real has the world of James Joyce's Ulysses become that it is hard sometimes to realise the oddness of the earnest debates as to whether Leopold Bloom was born in Clanbrassil Street Upper or Clanbrassil Street Lower (actually, he wasn't born at all).
Joyce chose to tie his fiction so securely to an actual time and place that one of its effects is a fruitful blurring of the gap between art and life.
It is an aspect of the democratic inclusiveness of Ulysses that, while many of its literary techniques are strange and "advanced", they are grounded in a thoroughly recognisable, Irish world. Even though the physical infrastructure of 1904 Dublin has drastically altered, the people remain our contemporaries 100 years later.
Some of the issues that the book raises also remain very contemporary. Its hero, Leopold Bloom, is an outsider, ethnically and culturally. There is a certain irony, for us, now, in the exchange in which Bloom, under hostile pressure, is asked what his nation is. "Ireland", he replies. "I was born here. Ireland." For Bloom, that settles the matter. Following the result of Friday's citizenship referendum, the answer is not quite so simple. It seems clear that this country still stands in need of the more inclusive vision of Irishness that Ulysses promotes - its message remains as relevant as in 1922, when it first appeared.
That inclusive vision was based on Joyce's own long experience of life on the European continent. It is customary to refer to the forces that drove him into voluntary exile from the age of 22. Today, of all days, it is appropriate to look at the other side of the equation: the positive experience of other lands which underpins the extraordinary diversity of his masterpiece.
Beneath Molly's final "yes" at the end of Ulysses is the rubric "Trieste - Zurich - Paris". These are the three cities in which the book was written (not one word of it was composed in Dublin, the city with which it obsessively deals). It would be unrealistic not to acknowledge the importance of Joyce's European experience on the work we are celebrating today.
Apart from everything else, Joyce has given Ireland an alternative feast day. And it should be celebrated because Ulysses is itself a celebratory book, the product of a comic, optimistic vision. That vision is forged out of unpromising materials - poverty, narrow and circumscribed lives, alienation - and the great achievement of Ulysses is that it remains true to the reality of those lives while also finding a means of liberating them. There is plenty of reason to rejoyce.