This PR targets a parsing inconsistency for `SimpleDateFormat` when using
explicit `dstOffset`.
Currently, `SimpleDateFormat` formatting applies the explicit `dstOffset` logic
when applicable. However, parsing does not consult the explicit `dstOffset`,
and uses the name in the text to derive whether daylight is in effect or not.
This can create round trip inconsistencies.
For example,
// Historical daylight offset: +00:34:39
Date.from(Instant.parse("1916-07-15T00:00:00Z")),
// Formats to -> 1916-07-15 00:34:39 Greenwich Mean Time
// -------------
// Historical standard offset: −00:25:21
Date.from(Instant.parse("1916-01-15T00:00:00Z")),
// Formats to -> 1916-01-14 23:34:39 Greenwich Mean Time
Both formatting calls produce "Greenwich Mean Time" in the text, even though
the first is in daylight. The second case can round trip because because it
uses the name to determine standard time. For the first case, the old code uses
"Greenwich Mean Time" to determine standard time during parsing, even though
the offset at that date is in daylight time. This produces the mismatched
`Date`s. This PR updates the parsing path to not set the `DST_OFFSET` based on
the name, but rather let the `Calendar` naturally derive the correct offset
from the zone when an explicit `dstOffset` is used.
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Interim AI Policy](https://openjdk.org/legal/ai).
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Commit messages:
- init
Changes: https://git.openjdk.org/jdk/pull/33235/files
Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=33235&range=00
Issue: https://bugs.openjdk.org/browse/JDK-8392991
Stats: 366 lines in 3 files changed: 203 ins; 153 del; 10 mod
Patch: https://git.openjdk.org/jdk/pull/33235.diff
Fetch: git fetch https://git.openjdk.org/jdk.git pull/33235/head:pull/33235
PR: https://git.openjdk.org/jdk/pull/33235
