WIP: Cookbook example showing how to handle icalendar time zones

[ptomato]

This is an example of how a ZonedDateTime object with a custom time zone could work, if TimeZone objects are removed. (#2853)

This shows integration with ical.js. It's a ZonedDateTime-wrapper object that internally maintains a real Temporal.ZonedDateTime object, but it takes an ICAL.Timezone instead of a Temporal.TimeZone. If the ICAL.Timezone object has the ID of an IANA time zone, we delegate everything to the real Temporal.ZonedDateTime and use the host's time zone database. If the ID is not an IANA ID, we fall back to the ICAL.Timezone's VTIMEZONE data.

Draft; still needs test data with which to make sure everything works, and a cookbook page.

[justingrant]

Thanks for doing this, seems like a reasonable starting point.

[justingrant]

Will this break around DST transitions that PDT is unaware of? That may be OK for a cookbook sample, but it may deserve a comment.

[ptomato]

I don't think it'll break. this.#impl.toPlainDateTime() will be unaware of any DST transitions at all, but adding this.offsetNanoseconds will correctly account for DST transitions in the VTIMEZONE.

[ptomato]

@justingrant If iCalendar is removing the custom time zone stuff from their specification after all, should we delete this example? Replace it with something else? Combining it with #1370 might be the best option, in that case.

[justingrant]

@justingrant If iCalendar is removing the custom time zone stuff from their specification after all, should we delete this example?

It's JSCalendar not iCalendar that's removing support for custom time zones, so that you can provide a time zone name only. In iCalendar AFAIK all time zones are custom-ish; you must supply time zone rules, not just a name.

Replace it with something else? Combining it with #1370 might be the best option, in that case.

Maybe have one sample that does both? AFAIK the rule semantics are similar even if the syntax is different.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 96.85%. Comparing base (2a9fec8) to head (99ced20).
Report is 11 commits behind head on main.

Additional details and impacted files

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  Files          21       21           
  Lines        9983     9983           
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  Hits         9669     9669           
  Misses        268      268           
  Partials       46       46           

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