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https://issues.apache.org/jira/browse/ORC-2151?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Gang Wu resolved ORC-2151.
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Resolution: Fixed
> 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
> Priority: Major
> Fix For: 2.3.1
>
>
> 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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