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Comment by userbinator | Hacker News Reader

I'm very curious how a bug like this could even happen. At a glance it doesn't appear to be the classic "ISO week-based year" problem discussed on HN a few times before, but somehow the code thinks Feb 1 2019 is a Wednesday... weeks starting with Sun vs Mon wouldn't account for the off-by-2 error seen here.

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I looks as if they started their calendar year with January 1st on Sunday. Maybe they just never even bothered to align the dates with the week days.

I’ve been scratching my head about this too. I can’t find a way to introduce such a bug in a date picker. The only one I’m thinking is a off by one when reading the month/year.

For example an API with 0-11 months, and one with 1-12. You’d get info of the wrong month.

Can't be the month, it has the right number of days.

Can't be the year, 2018 and 2020 also don't have February 2 on Thursday.

It can't even be the month but only for the starting day, neither January nor March have their 2nd on a Thursday.

Could've been hardcoded for an older year for a deadline? Never got implemented to use the correct calendar based on the year?

I sure hope not, because in that case that thing has been broken for the whole 2018!

According to that Twitter thread, it has been broken for 2 years.

As another comment pointed out, just try it with a 2-digit year: https://www.timeanddate.com/calendar/monthly.html?year=19&mo...

It's stupid to not have a yyyymmdd format anyway. The American mmddyyyy format causes a lot of confusion.

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