Time-zone database issues

Naoto Sato naoto.sato at oracle.com
Thu Oct 25 15:17:36 UTC 2018

Thanks, Stephen.

I filed an issue for your suggestion:


I will need to look into the issue, but so far as I understand, will it 
be fine to modify the offending transition date to the next day for 
2018f's immediate issue?


On 10/22/18 3:25 PM, Stephen Colebourne wrote:
> The IANA time-zone database [1] provides details of how time-zones
> change over time. The latest release - 2018f - cannot be processed
> successfully by the current JDK parser [2].  A workaround exists
> however unlike previous cases of tzdb incompatibility, this time it
> makes sense for the JDK parser and API to be changed.
> Problem
> -----------
> The JDK parser and API make the assumption that a time-zone change can
> occur at any LocalTime or midnight-end-of-day, ie. from 00:00 to
> 24:00. Unfortunately, the tzdb source files allow (and now include)
> rules outside those valid values, in this case a value of 25:00.
> Specifically, the rule that causes problems says that clocks change at
> 25:00 on the first Saturday on or after the 8th of September.
> In the current problematic case, the rule can be rewritten to say that
> clocks change at 01:00 on the first Sunday on or after the 9th of
> September. However, there are cases where it is difficult to
> impossible to rewrite the rule (such as 25:00 on the last Saturday in
> a month, difficult because it goes into the next month).
> Proposed solution
> ------------------------
> Fixing the parser to handle values like 25:00 would be relatively
> easy. However, these rules are also exposed in the public API of
> java.time.zone.ZoneOffsetTransitionRule [3]. Currently this class has
> methods `getLocalTime()` and `isMidnightEndOfDay()`. These would need
> to be deprecated and replaced by a new method `getLocalTimeDuration()`
> (or some other name) that returns an instance of `Duration`.
> A user of ThreeTen-Backport [4] has provided a branch to do this, so I
> know the change to be possible. However, since I have looked at the
> code I cannot implement the change in OpenJDK (compromised IP). It
> needs a cleanroom implementation by someone else.
> Is there agreement on the need for change? Is anyone (Oracle or
> otherwise) willing to volunteer do the work?
> thanks
> Stephen
> [1] https://www.iana.org/time-zones
> [2] https://bugs.openjdk.java.net/browse/JDK-8212684
> [3] https://docs.oracle.com/en/java/javase/11/docs/api/java.base/java/time/zone/ZoneOffsetTransitionRule.html
> [4] https://www.threeten.org/threetenbp/

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