People went to bed on the 4th of October 1582 and woke up on the 15th. The days in between were deleted.
The Julian calendar ran about eleven minutes long each year. Harmless, until sixteen centuries of it stacked into a ten-day drift against the seasons. Pope Gregory XIII fixed it by cutting ten days out of the calendar.
Not everyone switched at once. For nearly two centuries, crossing a European border could move you ten days forward or back. Britain held out until 1752, by which point it had to delete eleven days, and riots followed over lost wages — people felt as though their lives had been shortened.
Sweden bungled its transition so badly it had to invent an extra day to climb out of it. February 30th, 1712. A date that exists nowhere else in history.
Calendars change. Human nature doesn't.
Time isn't fixed. We fix it.