An explaination, Mr. Taoiseach?

This is a few days old, but I cannot remain silent any longer. The yearly "Shamrock ceremony" at the White House every March 17th really bothers me. Why does the Prime Minister of Ireland come here every year on the day of his nation's largest holiday to give us a bowl of clover. Everything about this tradition is backwards. If anything, our president should visit them and bring the taoiseach a gift to thank Ireland for contributing immigrants who produced so many fine citizens like myself. It is their holiday-- can you imagine if every 4th of July our president skipped the fireworks and went to London to give the queen a hamburger? It would make no sense. Furthermore, the whole enterprise seems to be cloaked in mystery, I cannot find a reasonable explanation for it anywhere online. Every article is just some boring mention of the "annual gesture of kinship" between the US and Ireland. This year the ceremony did actually take place on the 16th, but it is the first time I've noticed it being moved up a day. If NPR can't figure it out, I'm stumped.