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Why are 2025/05/28 and 2025-05-28 different days in JavaScript?

brandondong.github.io

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Re: Why are 2025/05/28 and 2025-05-28 different days in JavaScript?

#12

Post by tluse »

Y_Y wrote: post #7

Hang on, slashes and year-month-day? https://en.wikipedia.org/wiki/ISO_8601 Handed down by the ISO, The Great Compromise allows YYYY-MM-DD (or YYYYMMDD if you're in a hurry) but the version with slashes I'd find ambiguous and upsetting, especially early in the month. The standard is good, and you can get it from `date -I`. Hell mend anyone who messes with the delimiters or writes the year in octal or any other heresy…

Pro tip: never ever use anything but ISO dates in UTC tz unless you're displaying it for a user in a UI.

Re: Why are 2025/05/28 and 2025-05-28 different days in JavaScript?

#14

Post by aloha2436 »

Y_Y wrote: post #10
yen223 wrote: post #8

Earlier quoted context omitted.

The world where JavaScript has a robust standard library is one where there is only one browser vendor who gets to call all the shots regarding what the web looks like. That is not a better world.

> That is not a better world. Not a better world, just the current world.

Safari is too valuable of a platform for web developers to ignore, but otherwise yes it's the only real exception to the Chrome monopoly and still certainly much smaller in terms of absolute users.

Re: Why are 2025/05/28 and 2025-05-28 different days in JavaScript?

#18

Post by xiconfjs »

tluse wrote: post #12
Y_Y wrote: post #7

Hang on, slashes and year-month-day? https://en.wikipedia.org/wiki/ISO_8601 Handed down by the ISO, The Great Compromise allows YYYY-MM-DD (or YYYYMMDD if you're in a hurry) but the version with slashes I'd find ambiguous and upsetting, especially early in the month. The standard is good, and you can get it from `date -I`. Hell mend anyone who messes with the delimiters or writes the year in octal or any other heresy…

Pro tip: never ever use anything but ISO dates in UTC tz unless you're displaying it for a user in a UI.

Even then it‘s ok :)

Re: Why are 2025/05/28 and 2025-05-28 different days in JavaScript?

#19

Post by nssnsjsjsjs »

tluse wrote: post #12
Y_Y wrote: post #7

Hang on, slashes and year-month-day? https://en.wikipedia.org/wiki/ISO_8601 Handed down by the ISO, The Great Compromise allows YYYY-MM-DD (or YYYYMMDD if you're in a hurry) but the version with slashes I'd find ambiguous and upsetting, especially early in the month. The standard is good, and you can get it from `date -I`. Hell mend anyone who messes with the delimiters or writes the year in octal or any other heresy…

Pro tip: never ever use anything but ISO dates in UTC tz unless you're displaying it for a user in a UI.

And unless you need the original date, time and time zone.

Conversion to UTC is not injective e.g. when clocks change or politics happen

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