The Flag of England is a white rectangular field charged with a centered red St George’s Cross — a plain upright red cross whose vertical and horizontal arms meet at the center. It is simple and highly visible; the red symbolizes St George, the patron saint of England. Common flag proportions are $3:5$ (also $1:2$ is used) and the cross’s arm width is typically about one-fifth of the flag’s height. The design dates from the medieval period and has been used as an English national emblem since the Middle Ages; it was later incorporated into the Union Flag. The flag is popularly flown on St George’s Day (23 April), at sporting events and on public buildings.