1897, actually. It was designed for the First Zionist Congress, and was accepted as the movement’s official flag a year later.
Despite myths to the contrary, the Shield of David, as a symbol of the Jewish People, dates back to no earlier than the 17th Century. Surprisingly, it’s the blue stripes on the top and bottom that have the true ancient origin - they’re taken from the traditional Jewish prayer shawl, the tallit, which dates, in various forms, back to early biblical times.