Republic of China calendar
The ROC calendar follows the tradition of using the sovereign's era name and year of reign, as did previous dynasties of China.Chorographies and historical research published in mainland China covering the period between 1912 and 1949 also use the ROC calendar.The status of the Gregorian calendar was unclear between 1916 and 1921 while China was controlled by several competing warlords each supported by foreign colonial powers.After the Kuomintang reconstituted the Republic of China on 10 October 1928, the Gregorian calendar was officially adopted, effective 1 January 1929.Based on National Standards of the Republic of China CNS 7648: Data Elements and Interchange Formats—Information Interchange—Representation of Dates and Times (similar to ISO 8601), year numbering may use the Gregorian system as well as the ROC era.