The League of Ireland Premier Division is the top level division in the Republic of Ireland football league system. Contested by 12 clubs, it operates a system of promotion and relegation with the League of Ireland First Division. Seasons run from March to October, with teams playing 33 matches. Most games are played on Fridays, with a few games held on Saturdays and Sundays. Since 2010 the league is sponsored by SSE Airtricity and therefore officially known as the Airtricity League.