Zhang Jiawei created ORC-2151:
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Summary: Move the ORC-306 timestamp compensation before timezone
conversion to prevent incorrect DST offset lookup.
Key: ORC-2151
URL: https://issues.apache.org/jira/browse/ORC-2151
Project: ORC
Issue Type: Bug
Reporter: Zhang Jiawei
Previously, the -1 second compensation for pre-1970 timestamps (caused by
Java's truncating integer division in Timestamp.getTime()) was applied after
the writer-to-reader timezone adjustment. This means
writerTimezone.getVariant(writerTime) was called with an uncorrected writerTime
that could be 1 second larger than the true value. If this 1-second discrepancy
happens to cross a DST (Daylight Saving Time) boundary, the timezone lookup
would return an incorrect GMT offset, causing the final timestamp result to be
off by the entire DST shift (typically 1 hour) rather than just 1 second.
By moving the compensation to before the timezone conversion, we ensure that
getVariant() always receives the corrected wall-clock time, producing the
correct DST offset and an accurate final result.
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