In the last 20 years, I kept only two issues of daily newspapers. Can you guess the two dates and why ?

Update, the answer: two issues of french daily newspaper Libération. First one dated 20-aug-1991, photo of Boris Eltsine standing on a military tank, legend « "On peut construire un trône avec des baillonettes mais il est difficile de rester longtemps assis dessus" - Boris Eltsine 19 Août 1991 ». Second one dated 22-aug-1991, graphics design showing the top of Gorbatchov's head with his so typical nevus, legend « GUERI ! ». That was before the web guys, you won't find those online, and that event changed the whole world more than any other in the last thirty years.