How does Queen Margrethe’s long reign compare to other monarchs?

How does Queen Margrethe’s long reign compare to other monarchs?

Denmark's Queen Margrethe II celebrates a half century on the throne on Friday, but which monarchs around the world have had longer reigns?

Denmark’s Queen Margrethe celebrates 50th jubilee

Denmark’s Queen Margrethe celebrates 50th jubilee

IN PICS: Denmark’s Queen Margrethe marks centenary of return of southern region

IN PICS: Denmark’s Queen Margrethe marks centenary of return of southern region