Closed justingrant closed 3 years ago
Remembrance Day usually includes a two-minute silence at 11:00.
I suppose the discussion could be copied over here from today's notes and this issue be closed?
@mj1856 mentioned the use case of countries with one time zone and no DST, where DateTime matches the mental model. @pipobscure mentioned that it matches the mental model in other cases as well, when one is planning events for oneself.
@mj1856 mentioned the use case of countries with one time zone and no DST, where DateTime matches the mental model.
BTW, after thinking more about the single-country/single-timezone/no-DST use case and I think we should NOT recommend DateTime for this use case in the docs. Developers may choose to ignore our guidance and use DateTime anyways--just like they often do with localization advice--but my proposal would be to document a clear standard that recommends that developers who know the place should use LDT, even in cases like India and China.
Why?
toLocaleString
instead of ${month}/${day}/${year}
. For example, imagine a Chinese or Indian app that wants to build a per-user timezone feature to support expats around the world. With LDT, adding such a feature would require replacing a global Asia/Shanghai
constant with a per-user variable. With DateTime, the changes would be much harder and error-prone. (FWIW, I'm sensitive to this because my last company had to do an expensive rewrite of "founder code" that was erroneously written to assume a single time zone.)Asia/Shanghai
, but:
The double time standard is particularly observable in Xinjiang Television, which schedules its Chinese channel according to Beijing Time and its Uyghur and Kazakh channels according to Xinjiang Time.[12] Some ethnic Han population in Xinjiang might not be aware of the existence of the UTC+06:00 Xinjiang Time because of the language barrier.[13] . . . In 2014, Apple Inc. released an update to its iOS mobile operating system, which silently changed the default time for users in Xinjiang into Xinjiang Time. As some users in the area were using Beijing Time in their iOS before the update and set the alarm of their phones and tablets according to Beijing Time, the silent change caused some alarms to ring at a time later than expected, causing disruption in daily activity on the day after the changes.[15]
Thoughts?
I suppose the discussion could be copied over here from today's notes and this issue be closed?
I'd suggest that we leave it open and close it via a docs PR, perhaps the same PR that resolves #655 via a docs page that maps specific use cases to the right Temporal type for those cases. Until that PR lands, I think this issue could be a helpful honeypot to attract use cases from other commenters.
I'd suggest that we leave it open and close it via a docs PR, perhaps the same PR that resolves #655 via a docs page that maps specific use cases to the right Temporal type for those cases. Until that PR lands, I think this issue could be a helpful honeypot to attract use cases from other commenters.
I think it's been open long enough to attract use cases, so I PR-ed some brief use cases into the PDT docs in #1344.
Once LDT lands, we'll need to explain the difference to users between DateTime and LDT (or whatever their final names end up being). I think a good way to do this in the docs will be to list some example use cases where DateTime is needed and LDT isn't appropriate. Here's an initial draft. What should be added/removed?
Temporal.PlainDateTime
will often be used as an intermediate step before converting to/fromTemporal.ZonedDateTime
orTemporal.Instant
using the separate time zone. Examples:America/New_York
time zone, or a legacy system that always records date/time data in the server's time zone.2020-04-09T16:08-08:00
that have a numeric offset instead of an IANA time zone likeAmerica/Los_Angeles
. These strings can also be parsed byTemporal.Absolute
, but if you need to know the local date and time thenTemporal.DateTime.from
is required. To avoid DST bugs, the result must be converted to a real time zone before creating derived values viaadd
,with
, etc.Are there other use cases that the list above omits? We're not looking for convoluted cases where DateTime could be used... but rather what are common use cases where DateTime should be used as a best practice and where LDT isn't appropriate due to bugs, ergonomics, etc.?
Also, what are other examples besides the 4:20 4/20 holiday of a date/time event that should be evaluated the same in every time zone? I thought of a lot of holiday examples (e.g. new year's day) but IMHO those are more properly modeled using a
Temporal.Date
because they always start at the beginning of the day. What are more examples of intraday events that are the same everywhere?