Unification Day is a national holiday in Bulgaria, celebrated annually on September 6th. This holiday commemorates the unification of Eastern Rumelia and the Principality of Bulgaria on this day in 1885. Bulgarians felt that the decision of the Berlin Treaty was unfair, and over the following seven years, initially peaceful demonstrations gave way to rebellion and conflict. The Bulgarian Secret Central Revolutionary Committee was formed in February 1885, which organized events and revolts in towns in Eastern Rumelia, designed to assist in the unification process. On September 6th, 1885, Bulgaria and Eastern Rumelia declared their unification in the city of Plovdiv. The main celebrations of Unification Day in Bulgaria are held on the evening of September 6th in the city of Plovdiv, which was once the capital of Eastern Rumelia when it was an Ottoman province. During these celebrations, the President and Prime Minister of Bulgaria attend the official ceremony.