On February 14, 1918, the new Soviet government adopted the Grigorian calendar, which changed all dates. Dates in the 18th century were advanced by 11 days; in the 19th century, by 12 days, and in the 20th century, by 13 days.

Dates written in publications after 1918 concerning events that occurred before 1918 are normally given in both styles, e.g. Lenin's birthday is cited as 10 (22).4.1870. The new date is April 22, 1870. For Lomonosov's birth and death dates, 8 (19).11.1711-4 (15).4.1765.
IUrii Andropov's birthday: 2 (15).6.1914.

For NACO purposes, cite only the modern (later) form. If the change in date involves a change in years, also use the later date.