I remember being in Dublin during 1988 when we were all celebrating the Millennium. It was sort of a great joke among all the city's residents because the idea that Dublin was founded in 988 was based on pretty flimsy evidence. Dublin existed before 988. All that happened that year was that some Norse King came and set himself up as ruler and well, I guess, declared Dublin (re)born.
Dublin's founding in 988 may only be tenuously connected to anything real, but it is like a mathematical proof compared with New York's 400 anniversary celebrations this year. When was New York founded? Well, we were always taught it was founded by Peter Minuet when he bought Manhattan from the Indians for $24 in 1626. I think a few Dutch families may have settled there in 1625, but that's about it.
So, what happened in 1609 that merits celebrating? Well, Henry Hudson sailed up the (now) Hudson River. He may well have pulled into the right near the mouth of the river for a night's sleep on his journey north, but I don't know if you can call that founding a city.
Regardless, New York City is celebrating its 400th 'birthday' and the Dutch appear only too happy to join in. Of course, if the banking crisis gets any worse maybe the Dutch will take it back and then pursue the Indians for a refund.