[tz] OpenJDK/CLDR/ICU/Joda issues with Ireland change

Michael H Deckers michael.h.deckers at googlemail.com
Sun Jan 28 17:27:30 UTC 2018

On 2018-01-27 05:34, Clive D.W. Feather wrote:
> Guy Harris said:

>> "Daylight Saving Time" presumably refers to turning clocks forward.
> No. That's not stated anywhere in ISO C - it's an assumption you've made.

    What about a dictionary? Random House:

      daylight saving
      the practice of advancing standard time by one hour in the spring of
      each year and of setting it back by one hour in the fall in order to
      gain an extra period of daylight during the early evening.


      daylight-saving time
      time set usually one hour ahead of the local standard time, widely
      adopted in the summer to provide extra daylight in the evening. Also
      called (in the US) daylight time See also British Summer Time

    The current documentation of the tzdb interfaces agrees with these
    definitions (except for the restriction of the amount to 1 h in
    Random House). From (at least) 1993-01 until 2018c, inclusive, it
    says that the dst bit of tzdb indicates "summer time"; the claim
    "but we always meant dst to indicate non-standard time rather than
    summer time" is not tenable.

    Of course, tzdb may use the term "daylight-saving time" in
    their own specific meaning -- but this should be clearly stated
    in the documentation. And whether a change in the meaning of
    one common term (as opposed to, for instance, a new term and a
    clear-cut interface change) is a helpful upgrade path for the
    tzdb customers is not clear to me.

    Michael Deckers.

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