My favourite one of this kind is the Rockchip RK808 RTC, where the engineers thought that November had 31 days, needing a Linux kernel patch to this day that translates between Gregorian and Rockchip calendars (which are gradually diverging over time).
Also one of my favourite kernel patch messages: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/lin...
> Rockchip calendars
>.< haha i remember this
It's always November, isn't it? I've once made a log collection system that had a map of month names to months (had to create it because Go date package didn't support that specific abbreviation for month names).
As you might've guessed, it lacked November, but no one noticed for 4+ months, and I've left the company since. It created a local meme #nolognovember and even got to the public (it was in Russia: https://pikabu.ru/story/no_log_november_10441606)