I'm not French, but your comment just made me 'realise' that people who use 12h have the largest numbers when we on 24h have the smallest, almost like the 'start' is one o'clock. Weird.

Same :00 start happens with minutes on 12h though of course.

I think GP didn't mean to talk about time, has a point regarding months as I replied elsewhere. We represent the months numerically as 1-12, and I have recently found that annoying to work with.

12:00 should actually be 0:00 on the 12 hour clock, it belongs to the next 12 hour period. 11:59 PM is yesterday, 12:00 AM is one minute later, and falls on today. Same with noon, 12:00 PM comes one minute after 11:59 AM. When I see 12:00, I automatically convert that to 0:00, otherwise AM/PM doesn't make sense.

Indeed, months are 1 based, but it's never been a problem to eg compute which month it will be, say 9 months later: just sum and subtract 12, no need for a real modulo computation. It's probable I've never found it annoying because I don't need to perform this computation with more than 12 months.

Yeah, this is most familiar to me too. Still, I'd argue it's 1-based. 00:00 is a point in time, but the first second is between 00:00:00 and 00:00:01, and it's "00:00:01" when it has elapsed.

No?