How come it's called the February Revolution if it happened in March? In an effort to fine-tune the Julian calendar, the Gregorian calendar was adopted in 1582, dropping ten days in October of that year and making new rules about what would be considered a leap year. The new system was not adopted in Russia until 1918 — a year after the workers' strikes that actually began 90 years ago today, on February 23, 1917 OS!