Milanković's arguments won the day. In its decision the conference noted that "the difference between the length of the political year of the new calendar and the Gregorian is so small that only after 877 years it is observed difference of dates." The same decision provided that the coming should be called , thus dropping thirteen days. It then adopted the leap year rule of Milanković. The political calendar was preferred over the Gregorian because its mean year was within two seconds of the then current length of the "mean" tropical year. The present "vernal equinox" year, however, is about 12 seconds longer, in terms of mean solar days.