Given the following context:

One of the main results of the revolution in Zanzibar was to break the power of the Arab/Asian ruling class, who had held it for around 200 years. Despite the merger with Tanganyika, Zanzibar retained a Revolutionary Council and House of Representatives which was, until 1992, run on a one-party system and has power over domestic matters. The domestic government is led by the President of Zanzibar, Karume being the first holder of this office. This government used the success of the revolution to implement reforms across the island. Many of these involved the removal of power from Arabs. The Zanzibar civil service, for example, became an almost entirely African organisation, and land was redistributed from Arabs to Africans. The revolutionary government also instituted social reforms such as free healthcare and opening up the education system to African students (who had occupied only 12% of secondary school places before the revolution).The government sought help from the Soviet Union, the German Democratic Republic (GDR), and People's Republic of China for funding for several projects and military advice. The failure of several GDR-led projects including the New Zanzibar Project, a 1968 urban redevelopment scheme to provide new apartments for all Zanzibaris, led to Zanzibar focusing on Chinese aid. The post-revolution Zanzibar government was accused of draconian controls on personal freedoms and travel and exercised nepotism in appointments to political and industrial offices, the new Tanzanian government being powerless to intervene. Dissatisfaction with the government came to a head with the assassination of Karume on 7 April 1972, which was followed by weeks of fighting between pro- and anti-government forces. A multi-party system was eventually established in 1992, but Zanzibar remains dogged by allegations of corruption and vote-rigging, though the 2010 general election was seen to be a considerable improvement.The revolution itself remains an event of interest for Zanzibaris and academics. Historians...

answer the following question:

What day is celebrated on 12 January every year in the country that was powerless to intervene and nepotism? 

Zanzibar Revolution Day