26th July; anniversary of the publication of Unua Libro, the first book describing Esperanto
Esperanto Day (Esperanto: Esperanto-Tago) is a worldwide observance on 26 July, which celebrates the publication of Unua Libro, the first book in the Esperanto language, by the language's creator, L. L. Zamenhof on this day in 1887. The annual multi-day World Esperanto Congress is held around this time.
- "Esperanto Day" (PDF). Universal Esperanto Association. Retrieved 14 December 2018.