The flag of Tonga was adopted on November 4, 1875. The flag looks similar to the flag of the Red Cross. The flag was originally identical to that flag, but to avoid confusion, it was changed so that the red cross appeared as a canton of a red ensign, making it similar to the 17th century red ensign. The flag has been in use since 1864 but was officially adopted in 1875. The constitution of Tonga states that the flag shall never be altered.