The national flag of Greece, popularly referred to as the "blue and white" (, ) or the "sky blue and white" (, ), is officially recognised by Greece as one of its national symbols and has nine equal horizontal stripes of blue alternating with white. There is a blue canton in the upper hoist-side corner bearing a white cross; the cross symbolises Eastern Orthodox Christianity, the prevailing religion of Greece. The blazon of the flag is Azure, four bars Argent; on a canton of the field a Greek cross throughout of the second. The official flag ratio is 2:3. The shade of blue used in the flag has varied throughout its history, from light blue to dark blue, the latter being increasingly used since the late 1960s. It was officially adopted by the First National Assembly at Epidaurus on 13 January 1822.