A Word on the Origin of April Fools' Day

With April Fools' Day being today, we figured it might be a good time to look back on the humble origins of the pranky day, so we turned to a passage in our origins book: In the Beginning. Here's what we've got:
If someone tries to tell you today's tradition goes back to the switch from the Julian to the Gregorian calendar in 1582, feel free to call his bluff. What is true is that the calendar year used to start at the end of March under the Julian schematic. Legend claims that because news traveled slowly in those pre-Internet (and pre-TV, phone, and daily newspaper) days, a few rubes didn't get the message that the Julian calendar was, well, out-of-date — and they continued to celebrate the New Year around the first of April, three months late according to the new Gregorian rules. While this surely did happen, there's no evidence that April Fools' Day grew out of it.