This reminds me of a bit of historic trivia: In 1582 the length of a year was recalculated to be more accurate. The inaccuracy had grown to be 5 days and had led to all kinds of screwed up dates for events like Soltices, but had also made it hard to calulate Easter. Pope Gregory introduced the reformed calendar, now called the Gregorian Calendar.

Most of the world adopted it, but in some places the peasants rioted because they believed they were being cheated of their "days"!!

Russia kept the Julian Calendar, and by early 1900s they were 11 DAYS off. After the Russian Revolution their calendar was changed to match the rest of the world, but the Russian Orthodox Church still calculates Easter the old way, so it's usually a week or 2 weeks later than the rest of the world.