Moving is certainly stressful right now, but imagine dealing with that headache along with every other New Yorker moving on the same day? Believe it or not, this is how it used to be. From colonial times up until WWII, May 1st was Moving Day, the one day a year when people in New York City moved. It's said that the tradition came from the Dutch, who set out for Manhattan on May 1st and therefore celebrated each year by swapping homes on this day. Later, landlords had to notify their tenants of rent increases on February 1st, which would take effect three months later at 9am. Tenants waited until May 1st to move, and the streets would be filled with "moving vans," Long Island farmers' wagons led by horses, clogging up the city streets and creating complete pandemonium.
More on this curious history here