While the Federal District was ruled by the federal government through an appointed governor, the municipalities within it were autonomous, and this duality of powers created tension between the municipalities and the federal government for more than a century. In 1903, Porfirio Díaz largely reduced the powers of the municipalities within the Federal District. Eventually, in December 1928, the federal government decided to abolish all the municipalities of the Federal District. In place of the municipalities, the Federal District was divided into one "Central Department" and 13 delegaciones (boroughs) administered directly by the government of the Federal District. The Central Department was integrated by the former municipalities of Mexico City, Tacuba, Tacubaya and Mixcoac.

Answer this question, if possible (if impossible, reply "unanswerable"): When was the autonomy of the municipalities eliminated?
1928