context: Today, on the site of the martyrdom of the hot throne, there is the statue of The Virgin Mary, built by architect László Székely and sculptor György Kiss. According to the legend, during György Dózsa's torture, some monks saw in his ear the image of Mary. The first statue was raised in 1865, with the actual monument raised in 1906.  Hungarian opera composer Ferenc Erkel wrote an opera, Dózsa György, about him. His revolutionary image and Transylvanian background were drawn upon during the Communist regime of Gheorghe Gheorghiu-Dej. The Hungarian component of his movement was downplayed, but its strong anti-feudal character was emphasized. In Budapest, a square, a busy six-lane avenue, and a metro station bear his name, and it is one of the most popular street names in Hungarian villages. A number of streets in several cities of Romania were named Gheorghe Doja. Also, a number of streets in serval cities of Serbia were named "Ulica Doža Đerđa".Two Postage stamps were issued in his honor by Hungary on 12 June 1919 and on 15 March 1947, the latter in the "social revolutionists" series.
question: How many years was the time span between the issue of two postage stamps in honor of Dózsa György?
answer: 28