We are living through the year 2015 right now, and as you may know, 2015-100=1915. Exactly a century ago, Albert Einstein was completing his general theory of relativity.
Albert Einstein in Berlin, 1915
If you want a little bit more accurate timing, it was November 1915 when Einstein gave a PowerPoint-free presentation in front of the most important academy of sciences in the world – and the U.S. readers kindly forgive me that it wasn't the U.S. National Academy of Sciences but the Prussian Academy of Sciences in Berlin.
He began to write systematic papers in 1916 which is why we sometimes quote 1916 as the year when GR was born.
Albert Einstein wrote three papers on GR in 1916 and the first one appeared in March,
Albert Einstein 1916a. “Die Grundlage der allgemeinen Relativitätstheorie.” [Basics of the general theory of relativity], Annalen der Physik 49: 769–822. (CPAE 6, Doc. 30). Reprinted in translation on pp. 111–164 of (Lorentz et al. 1952).Now, 100 years later, things looks simple.
If you are waiting for a very short cartoon that "explains" GR in approximately 5 sentences and 10 semi-animated pictures, for a cartoon where Einstein looks like a brother of Superman who jumps from the skyscraper, open