Zamenhof Day (Esperanto: Zamenhofa Tago, Polish: Dzień Zamenhofa), also called Esperanto Book Day, is celebrated on 15 December, the birthday of Esperanto creator L. L. Zamenhof.It is the most widely celebrated day in Esperanto culture. On this day, Esperantists hold information sessions and cultural gatherings to promote literature in Esperanto.

The history of celebrating Esperanto on Zamenhof’s birthday can be traced back to 17 December 1878, when at a birthday party for his 19th birthday he presented to his friends his Lingwe uniwersala, the first version of his international language. By 1887, this language had evolved into what is now recognized as Esperanto when he published the Unua Libro. 15 December previously used to be also known as Esperanto Day,but that is now celebrated on 26 July, the day Unua Libro was published.

15 December 2009 marked 150 years since Zamenhof’s…