August 4, 2026
Time drama: canceled dates
Dates That Don't Exist (2015)
When 10 days vanished, coders turned it into a history-fueled comment war
TLDR: A post about the 10 calendar days skipped in 1582 exposed that some popular languages still let you create dates that never officially existed. Commenters turned it into a hilarious fight over whether those days are truly invalid, while others piled on with even weirder historical date glitches like Sweden’s February 30.
A delightfully nerdy post about the 10 days that never happened in October 1582 somehow turned into the internet’s favorite kind of chaos: people arguing about whether missing dates are really missing, while dragging programming languages for getting basic history wrong. The original point was simple enough: when much of Catholic Europe switched calendars, the day after October 4 became October 15. So if a program claims to use the modern calendar, dates like October 5, 1582 should be impossible. Ruby got applause for flat-out refusing them. Python and Perl? The comments basically handed them a giant "nice try" sticker.
But the real fireworks came from the replies. One commenter casually dropped that Swift doesn’t throw an error at all — it just teleports October 5 to October 15, which feels less like calendar handling and more like a time-travel prank. Another commenter kicked off the philosophy fight: is that 10-day gap an actual forbidden zone, or just a messy handoff between two systems? That split the room fast. Then, because the internet can always go deeper, someone brought up Sweden’s official February 30 in 1712, sending the thread spiraling into “oh no, dates are worse than we thought” territory. Even church history got fact-checked, with commenters correcting each other on who switched calendars, when, and whether it was even the same calendar at all.
The vibe? Equal parts history lesson, bug hunt, and communal realization that time is fake, software is fragile, and commenters will absolutely make it funnier.
Key Points
- •The article says the Gregorian reform in 1582 changed the year length assumption from 365.25 to 365.2425 days and introduced the modern leap-year rules.
- •To correct accumulated drift between the Julian and Gregorian calendars, the dates October 5 through October 14, 1582 were skipped in the Catholic world.
- •As presented in the article, October 5-14, 1582 do not exist within the Gregorian calendar system discussed.
- •Ruby rejects creation of an impossible Gregorian date such as October 5, 1582 by raising an invalid date error.
- •Python's datetime module and Perl's CPAN DateTime module are reported to allow impossible Gregorian dates without error.