Adoption of the Gregorian calendar for secular use occurred in Eastern Orthodox countries as late as the 20th century and some religious groups in some of these countries still use the "old style" (O.S.) Julian calendar for ecclesiastical purposes. The Kingdom of Bulgaria changed from the Julian to the Gregorian calendar during the First World War on 31 March 1916, where the next day was 14 April 1916. The Ottoman Empire's Rumi calendar, used for fiscal purposes, was realigned from a Julian to a Gregorian starting on 16 February/ 1 March 1917. The beginning of the year was reset to 1 January starting in 1918.
Adoption of the Gregorian calendar 1 for 1868, "Taishō" 1 for 1912, "Shōwa" 1 for 1926, "Heisei" 1 for 1989, and so on. Still, this system has increasingly been replaced in popular usage by the "Western calendar" (西暦, "seireki") over the course of the twentieth century. Korea adopted the Gregorian calendar on 1 January 1895 with the active participation of Yu Kil-chun. Although the new calendar continued to number its months, there were multiple systems used to refer to its years: during the Joseon Dynasty, in 1895–97, its years were numbered from the founding of that dynasty, regarding 1392 as year one; then between 1897