Among the many things to disappear during the world-shaking turmoil of the Russian Revolution—along with czarism, the aristocracy, private banks, landownership—were the first thirteen days of February. On 24 January 1918, Lenin signed a decree ordering the country to switch from the Julian calendar, used by the Orthodox Church, to the Gregorian, bringing revolutionary Russia into line with the rest of Europe. The two systems had been drifting more and more out of alignment since the sixteenth century, so much so that by 1918, making the change meant skipping directly from 31 January to 14 February. From then on, anyone referring to events that took place before this interregnum had to be clear whether the date they were using was Old Style or New Style. The shift also explains why the anniversary of the Great October Revolution was always celebrated in November, which often puzzled visitors to the USSR.
The 1918 calendar reform was an abrupt, one-off change, designed to signal the irreversibility of the leap from the ancien régime to the new. Undoing the revolution would now mean literally turning back time—which is what some upper-crust characters attempt to do in Sigizmund Krzhizhanovsky’s 1929 novella Memories of the Future when they ask the inventor of a time machine to take them back to the days of serfdom. Pushing the calendar forward was only one part, however, of a much broader campaign to sweep away backwardness and superstition and, in particular, to loosen the grip of religion on everyday life. Early on, the Soviets invented a series of ceremonies designed to replace Orthodox rituals: in addition to secular weddings and funerals, the government introduced “Octobering,” a Leninist alternative to baptism. There was also a weekly paper called Bezbozhnik—“Atheist,” “Godless One”—and, from 1925, a League of the Militant Godless.
more here.