|Thomas Nast caricature of Boss Tweed|
At the height of his power and influence, according to the linked Wikipedia article, Tweed was "the third-largest landowner in New York City, a director of the Erie Railroad, the Tenth National Bank, and the New-York Printing Company, as well as proprietor of the Metropolitan Hotel." Tweed made money the really old-fashioned way: He stole it from the taxpayers.
But Tweed was caught out in the end. He wound up dying in prison.
So we're not celebrating corruption on Tweed Day, we are really celebrating the (eventual) triumph of reform.
And April 3 will be World Party Day. This may be a microminiholidayette on the cusp of breaking through into popular consciousness: It has its own Wikipedia entry, Tumblr and Twitter page. Quoting from the Twitter page, World Party Day is an "annual celebration for a happy world." On April 3, "the whole world parties in synch."
We never knew.