International Women's Day is on March 8 because of a calendar difference during a 1917 Russian protest.

In 1917, Russia used the Julian calendar. This system was 13 days behind the Gregorian calendar used in most other parts of the world. On February 23, 1917, thousands of women in Petrograd left their jobs to protest. In the Gregorian calendar, this date was March 8.The protest grew quickly. By the next day, over 128,000 workers joined the strike. This movement led to the end of the Russian monarchy. The new government gave women the right to vote on July 20, 1917. Russia became one of the first large countries to allow women to vote.A government official named Alexandra Kollontai helped make the day an official holiday. In 1921, a meeting in Moscow officially picked March 8 to honor the strike. Before this, different countries celebrated women on different days. For example, the United States used the last Sunday in February.The calendar difference happened because the old Julian calendar was not perfectly accurate. It gained about 11 minutes of error every year. By 1917, those minutes added up to 13 full days. The Gregorian calendar fixed this error by changing how leap years work.