An estimated 2 million people around the world speak Esperanto, the first most widely spoken constructed language. These people annually celebrate Zamenhof Day on December 15. This is a very important holiday, that draws public attention to Esperanto.
Tea is one of the most popular beverages around the world. And it looks so natural to have a special day to celebrate it. By the way, here it is, International Tea Day, that every year falls on December 15.