Why does the use of the old Julian calendar in Russia create confusion in history writing?

Correct answer: Because dates of February and October Revolutions appear different in the new calendar

Russia used the Julian calendar until the government adopted the Gregorian calendar in 1918. The Julian calendar was behind the Gregorian calendar by thirteen days during the twentieth century. Consequently, an event recorded as 23 February in the old calendar was 8 March in the new calendar, and 25 October was 7 November. This is why the February and October Revolution names can appear to have dates that do not match modern records. Option A is correct.

The problem was not that Russians failed to count years, that the Tsar renamed every month, or that the Soviets erased dates. Historians must always check which calendar a source uses before comparing dates. The different names therefore reflect calendar conversion, not different events.