In 1972, Sibelius's surviving daughters sold Ainola to the State of Finland. The Ministry of Education and the Sibelius Society of Finland opened it as a museum in 1974. The Finnish 100 mark bill featured his image until 2002 when the euro was adopted. Since 2011, Finland has celebrated a Flag Day on 8 December, the composer's birthday, also known as the "Day of Finnish Music". The year 2015, the 150th anniversary of the composer's birth, featured a number of special concerts and events, especially in the city of Helsinki.