ShivanshhhG opened a new pull request, #54627:
URL: https://github.com/apache/arrow/pull/54627
### Rationale for this change
When formatting zoned timestamps whose UTC offset includes sub-minute
seconds (e.g. historical IANA zones such as `Africa/Monrovia` prior to 1972 at
UTC-00:44:30 or `Europe/Paris` prior to 1911 at UTC+00:09:21), the vendored
`date.h` library truncated the offset to whole minutes via
`duration_cast<minutes>`, omitting the remaining seconds and emitting an
inaccurate offset (e.g. `-0044` instead of `-004430`). When parsed back (via
`Cast` or CSV reader), the timestamp instant was shifted by up to 59 seconds.
### What changes are included in this PR?
1. **`cpp/src/arrow/vendored/datetime/date.h`**:
- In `to_stream` for format specifiers `%z` and `%Ez`, check whether
`*offset_sec` has non-zero seconds (`s != 0`).
- If non-zero seconds are present, emit them (`±hhmmss` for `%z` or
`±hh:mm:ss` for `%Ez`). If whole minutes, retain the standard `±hhmm` /
`±hh:mm` representation.
2. **`cpp/src/arrow/util/value_parsing.h`**:
- Added `detail::ParseHHMMSS` to parse 6-digit offsets with hours,
minutes, and seconds.
- Updated `ParseTimestampISO8601` to recognize and parse `[+-]HHMMSS` and
`[+-]HH:MM:SS` zone offsets.
3. **`cpp/src/arrow/util/value_parsing.cc` &
`cpp/src/arrow/compute/kernels/scalar_temporal_unary.cc`**:
- Updated `StrptimeTimestampParser` and `GetZone` to recognize `%Ez` as
providing a zone offset.
4. **Tests**:
- Added unit test cases for sub-minute offsets and invalid offsets in
`cpp/src/arrow/util/value_parsing_test.cc`.
- Added regression test cases casting zoned timestamps in
`Africa/Monrovia` and `Europe/Paris` to strings in
`cpp/src/arrow/compute/kernels/scalar_cast_test.cc`.
### Are these changes tested?
Yes, new unit tests were added to `value_parsing_test.cc` and
`scalar_cast_test.cc`.
### Are there any user-facing changes?
Yes, casting zoned timestamps with sub-minute UTC offsets to string (and
exporting them to CSV) now accurately formats the offset seconds rather than
truncating them, and `ParseTimestampISO8601` can parse timestamps with seconds
in the UTC offset.
* GitHub Issue: #54534
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