The league is a subsidiary unit of length in the British Imperial system, the longest unit in this system, defined as 5280 yards. The British Imperial system of units was established on June 17, 1824, by the Weights and Measures Act. Strictly speaking, it is not correct to use the term British Imperial for units in use before that date, and they are better described as traditional British. In this system, the standard yard had a length of 0.914398416 m, making the league equal to 4828.02363648 m. (Cardarelli gives a value of 0.91443992 m, but this is in error.) For the detailed history of this yard, see Yard (British Imperial).