Rubber Eraser Day
Rubber Eraser Day is held on April 15. Joseph Priestley discovered the eraser in 1770, using pieces of rubber imported from Brazil. Then in 1858, Hyman Lipman of Philadelphia, Pa., patented the pencil with an eraser at the end. This event in the second decade of the month April is annual. 
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Tablets of rubber (or wax) were used to erase lead or charcoal marks from paper before there were rubber erasers. Another option for the eraser was crustless bread. Pencils with built-in erasers on the tops are a largely American phenomenon.
An eraser isn’t called eraser by eraser manufacturers, either. Their name for the little erasers on pencil ends: “plugs!”
More and more of today’s erasers are made from something other than rubber! While some of the “pink” erasers you find on pencils are made from synthetic rubber blended with pumice (a grit that enhances its ability to erase), an increasing number of erasers are made from vinyl. Vinyl is a type of durable, flexible plastic.
Similar holidays and events, festivals and interesting facts
International Moment of Laughter Day on April 14 (is focuses on laughter as a way to de-stress);
Look Up at the Sky Day on April 14
Reach as High as You Can Day on April 14
That Sucks Day on April 14 (Throughout the history of the holiday and the organization that sponsored it, That Sucks LLC, they seek to exemplify all that is terrible and wrong in the world);
N'Ko Alphabet Day on April 14 (Mande speakers);
Wine Journalist's Day in Argentina on April 14
Take A Wild Guess Day on April 15
Stoker's Day on April 15 (is celebrated in spring, at the end of the heating season. All shifts workers gether in the boiler room to extinguish the boilers and begin to celebrate. The date of this celebration is not fixed. The local authorities decide when to start and when to finish the heating season but usually it hapends not later than April 30 if the average air temperature is above +8 for 3 days in a raw);
Foursquare Day on April 16
Wear Your Pajamas To Work Day on April 16
National Tickle Day in USA on April 16