"Stapler invented on this day in 1868". That's what my event calendar says, and it looks so simple. But what does it mean for something to be invented on one day? Does that mean that the inventor thought up the idea and created a prototype in 24 hours? Even if someone did, it wasn't in 1868; apparently Louis XV of France had a stapler in the 18th century. Patents are often used as a proxie for invention, and it turns out that on this date in 1868, a patent was issued in England to Charles H. Gould for a wire-stitching machine for binding magazines that cut a piece of wire, bent it, stabbed it through paper, and folded the ends over; this machine is generally considered to be the forerunner of the modern stapler. But the "birthdate" of the familiar stapler might be better considered to be February 18 (or 12th, depending on the source), 1879, when a patent was issued for the McGill Single Stroke Staple Press, a two-and-a-half-pounder which could load a single staple and drive the staple through several pieces of paper. Inventing machines like this tends to be a messy business, with lots of incremental improvements (and patents for same) over a series of years before the machine takes on a stable form, so it seems a little artificial to pick one patent out of the progression and call it the "official" invention date.
For more on how things like the stapler are invented, see The Evolution of Useful Things, by Henry Petroski, a neat geeky book on "how everyday artifacts - from forks and pins to paper clips and zippers - came to be as they are."