In the year 1582, 4th Oct was followed by 15th Oct - The Story behind those 10 Missing Days
In 1582, something peculiar occurred: Thursday, october 4th, was followed immediately by Friday, october 15th, skipping 10 days entirely. This was the result of the introduction of the Gregorian calendar by Pope Gregory XIII, replacing the older Julian calendar, which had been used for centuries. The Julian calendar, established by Julius Caesar in 46 B.C., miscalculated the length of a solar year by about 11 minutes. Over the centuries, this slight inaccuracy caused a drift in dates, pushing important events like the spring equinox further from their intended place on the calendar.
By the 16th century, this drift had shifted the equinox by about 10 days, which affected the timing of religious observances like Easter. To correct this, Pope Gregory XIII issued a papal bull in february 1582, ordering the adjustment of the calendar. To bring the dates back in line, 10 days were removed, and the calendar was reformed to prevent further drift by altering the leap year rule.
The change was initially adopted by Catholic countries like Italy, Spain, and Portugal, but Protestant and Orthodox nations were slower to adopt it, leading to calendar differences between countries for centuries. The "10 missing days" represent a pivotal moment in timekeeping history, data-aligning the calendar with astronomical realities.