During the 1908 Olympics in London, the Russians showed up 12 days late due to the fact that they were using the Julian calendar instead of the Gregorian calendar.

The Extra Mustard Trivia Hour: When a Calendar Defeated Russia in the 1908 Olympics

If you were to turn your calendar to January 7th, you’d likely see the words “Christmas (Eastern Orthodox)” or something similar on that date. To those of you who celebrate it, Merry Christmas! Everyone else, you’re probably wondering why there’s an entire religion that observes Christmas weeks after you do.

The reason for the discrepancy? Partially, it’s Julius Caesar’s fault. Over 2,000 years ago, he promulgated the Julian calendar, a base-365 day calendar that erred in its accounting for leap years. As time progressed the calendar fell out of sync with the seasonal equinoxes; before long, Easter, in particular, wasn’t where it should have been. Finally, in 1582, Pope Gregory XIII had enough of this and mandated that Catholic nations … Continue Reading

Source: https://www.si.com/extra-mustard/2013/12/30/the-extra-mustard-trivia-hour-when-a-calendar-defeated-russia-in-the-1908-olympics?utm_source=reddit.com