[tz] New IANA-timezone support date/time library

Brian Park brian at xparks.net
Mon Feb 22 18:04:48 UTC 2021

Thanks for the info. I scanned through the Readme page, but I couldn't find
the answer to my question: Does your library have the ability to set the
underlying database to a specific TZDB version (e.g. 2019f, 2021a)?

I would like this feature to get deterministic functional testing, instead
of having the OS change the underlying TZDB version underneath me. The
HowardHinnant C++ date library (https://github.com/HowardHinnant/date) is
the only library that I know that has this feature. I am looking for a
second library.

On Mon, Feb 22, 2021 at 9:32 AM Kerry Shetline via tz <tz at iana.org> wrote:

> I’ve just finished an extensive update of a JavaScript/TypeScript
> date/time library that I’d previously used only for my own astronomy
> website, skyviewcafe.com. I’ve done enough updates to this library now
> that it may be of interest to many other software developers, especially if
> they want to handle the odd edge cases that exist in timezone handling,
> like 47-hour days and missing days and the like. One unique features is
> that it's possible for users to get live updates of the tz database, which
> usually don’t become available to applications without, at the very least,
> restarting an application, if not rebooting one’s computer.
> Libraries in this category are hardly unique, but one of the most popular
> libraries, Moment.js, is being phased out, so this seemed to be to be a
> good time to introduce a new one.
> Among the (possible) unique features, you can do things like find the
> specific moments of DST transitions and other transitions, like UTC offset
> changes, and get descriptions of these changes, like this:
> new DateTime('2021-11-07', 'America/New_York').getDiscontinuityDuringDay()
>> { start: '02:00:00', end: '01:00:00', delta: -3600000 } // fall back!
> // As soon as it’s midnight on the 30th, it’s instantly midnight on the
> 31st, erasing 24 hours:<br>
> new DateTime('2011-12-30', 'Pacific/Apia').getDiscontinuityDuringDay()) →
> { start: '00:00:00', end: '24:00:00', delta: 86400000 }
> // As soon as it’s midnight on the 31th, turn back to 1AM on the 30th,
> adding 23 hours to the day:<br>
> new DateTime('1969-09-30',
> 'Pacific/Kwajalein').getDiscontinuityDuringDay() →
> { start: '24:00:00', end: '01:00:00', delta: -82800000 }
> My updated library can be found here:
> https://www.npmjs.com/package/@tubular/time
> Besides the IANA timezone support, this library also features the ability
> to handle variable switch-over from the Julian to the Gregorian calendar,
> which can be of helpful to those handling historical dates.
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